Skip to main content

Full text of "Evolution of the color pattern in the microlepidopterous genus Lithocolletis"

See other formats


L- 



n 



Evolution of the Color Pattern in 

the Microlepidopterous Genus 

Lithocolletis 














BY 



ANNETTE FRANCES BRAUN 



PHILADELPHIA 
1914 



EVOLUTION OF THE COLOR PATTERN IN THE MICROLEPI- 
DOPTEROUS GENUS LITHOCOLLETIS. 

By Annette Frances Braun. 



CONTENTS. 

I. Introduction 105 

II. Methods and Observations 106 

(a) Systematic Position and Characteristics of Lithocolletis 106 

(6) Color Classes Represented and Structure of Scales 109 

(c) Comparative Study of the Adult Markings 110 

{d) Ontogenetic Development of the Color Pattern 118 

1. Historical 118 

2. Methods 121 

3. Observations 123 

4. Discussion and Conclusions 141 

(e) Phylogenetic Development of the Color Pattern 149 

III. General Discussion 160 

IV. Summary ^ 164 

I. INTRODUCTION. 

The interest in a study of the origin of the many and complex forms of color 
pattern in insects hes mainly in the hope that such a study may give additional 
insight into the fundamental principles of evolution in general. With few 
exceptions, such as the work of Tower on Leptinotarsa, researches of this nature 
have been confined to the Macrolepidoptera, chiefly to the butterflies and higher 
moths. The Microlepidoptera, which are less advanced from the viewpoint 
of evolution, have been almost neglected. Yet, within this group, several of 
the older and larger genera afford excehent and ample material for such an 
investigation. To secure convincing data, a critical study, both ontogenetic 
and phylogenetic, must be made of the species of a large genus, in which the 
color patterns, while sufficiently diverse to indicate that a considerable degree 
of evolution has taken place, are still comparatively simple. 

The genus Lithocolletis fulfills to an extraordinary extent these require- 
ments; hence the following investigations were undertaken with the object of 
ascertaining the modes of origin of the various color patterns in this genus and 
the influences which have been operative in their evolution. The study of 
adult color patterns has extended over a period of several years; the observa- 
tions on pupal development were made during the summer of 1910. 

It is a pleasure to express to Prof. M. F. Guyer my appreciation of his 
many helpful suggestions during the progress of my work. 



106 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

11. METHODS AND OBSERVATIONS. 
(a) Systematic Position and Characteristics of Lithocolletis. 
The genus Lithocolletis belongs to the large family Tineidse of the Micro- 
lepidoptera. It comprises a large number of very small moths, varying in 
expanse from 4 to 12 mihimeters. The larvae are exclusively miners, usually in 
leaves or very rarely in the bark of stems. The entire larval and pupal existence 
with one or two exceptions is passed within the mine. The genus, as originally 
estabhshed, has a remarkably uniform structure and a very characteristic 
appearance, enabling one to recognize the species easily. The structural char- 
acteristics which distinguish the typical and principal group are the fohowing: 

,^ IP 9 ^ Face smooth; crown tufted; labial palpi por- 

^-^^^^^ rected or drooping, moderately long and pointed; 
maxillary palpi rudimentary; tongue of moderate 
^^.^^^^^^^^^ length; antennae nearly attaining the wing length, 

^^^^^^^^^=^ simple in the male, basal joint thickened and bearing 

FiG.'i. Nen^iionoiLithocoiieUs. ^ P^^.^^^' ^hc forewiugs are elongate, lanceolate, 

acuminate. The hindwings are about one-half the 
breadth of the forewings, linear lanceolate and fringed with ciha whose length 
is from four to five times the breadth of the wings. The venation is illustrated 
by Fig. 1;^ forewings, lb simple, 3 absent, 4 absent, 6 absent, 7 to costa, 8 ab- 
sent, 11 absent; hindwings, 3 absent, 4 absent, transverse vein absent between 2 
and 5, 6 absent. The posterior tibiae bear appressed hairs. 

All of the European species and the great majority of the American species 
conform to the above conception of the genus. There are, however, in North 
America a few species belonging to two different groups, which differ structurally 
from the typical species; for these, two subgenera, Porphyrosela 
and Cremastobomhycia have been erected (Braun, '08). The 
former of these, Porphyrosela, differs from Lithocolletis in the 
absence of vein 10 of the forewings, the absence of a pecten on 
the first joint of the antennae and in the absence of hairs on the 
hind tibiae.^ It thus represents a later development, phylogen- of porphyrosela 
etically, in the direction usually taken in this family; that is, 
a reduction in the number of veins (Fig. 2). Cremastobombycia is of a more 
ancestral type than the typical Lithocolletis; it possesses an additional vein in 
each wing; on the forewing, vein 4 is present and stalked with 5; on the hind- 
wing, vein 6 is present and long stalked with 5 {Fig. 3) . 

In the European fauna, the typical Lithocolletids are a very homogeneous 
group of species both as regards larval characteristics and imaginal markings. 

1 References in italics are to the text figures, those in Roman type to the figures on the 
plates. 

2 Since this paper was written, studies on very closely allied species have shown that these 
characters are not sufficiently constant to define a genus (Meyrick, Genera Insectorum, 128me 
Fascicule, p. 5, 1912). Vein 10 is probably faintly visible in large specimens of L. desmodiella. 




10 g 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 107 

In all, the larva is of the so-called cyhndrical type, which agrees well with the 
usual type of lepidopterous larva. During the first three instars, in which the 
extent of the mine is gradually increased by a loosening of one epidermis, the 
larva has a characteristicahy flattened shape, with flat 
head and projecting mouth-parts. After the third moult, 
the larva assumes the normal cylindrical shape and the 
mine becomes tent-hke by a fold in the loosened epider- ^S^TITb'^ 
mis. The larva then consumes the greater part of the ^S^S^^fc=^ 
parenchyma within the area occupied by the mine. The 
pupa, except that of one species, is always formed within maMoinhydT 
the mine and may or may not be enclosed in a cocoon. 

The forewings of the imagoes are marked by various combinations of white 
transverse fascise and streaks on a yellowish ground color. These white marks 
are bordered along their inner edges by dark brown or blackish scales; some- 
times, but to a less extent, dark scales may also appear along their outer edges. 
The hindwings are unicolorous. 

Our American species while conforming in all structural characteristics to 
those of Europe, fall naturally into two groups; one of these agrees closely in 
structure of larva and imaginal markings with the European type just described; 
the other has what has been termed the ^^flat larva,'' and the imagoes produced 
from such larvae can always be sharply distinguished by their markings from the 
species of the ''cylindrical-larval group.'' The ''flat larva" retains the flat 
shape, which is characteristic of the first three instars of the "cylindrical-larval 
group," through the fourth, fifth and sixth instars, only assuming the cylindrical 
shape and an approach to normal mouth-parts with the last moult. By some 
systematists, the persistence through three additional larval instars of the curious 
modification of the mouth-parts, which is in fact an adaptation for loosening 
the epidermis, has been regarded as a sufficient ground for the generic separation 
of this group, and the name Cameraria Chapman has been applied to it (Chap- 
man, '02). The other view, which regards the modification of the mouth-parts 
merely as an adaptation for a particular mode of life, and not a character indi- 
cating the natural separation of that group from one with which the imagoes 
agree in all structural details, has been presented in the Canadian Entomologist 
for December, 1909 (Braun, '09). 

The mines of the "flat-larval group" are alwa^/^s found upon the upper side 
of the leaf. The increase in the extent of the mine continues through six instars, 
the larva consuming only a few layers of cehs in front of it. For this reason, 
the parenchyma within the mine is never entirely consumed and the mine 
rendered semitransparent, as is the case in mines of the " cyhndrical-larval 
group." During the seventh instar, the larva does not feed; the time is occupied 
in preparation for the pupal state. Where the imago is to emerge the same 
summer, most of the species spin cocoons. The cocoon is a flat, oval sheet of silk 
attached around its edge to the floor of the mine, the epidermis above being 



108 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

thrown into a fold. In the overwintering generation^ the larvse hibernate, 
changing to pupse in spring without spinning cocoons. The characteristic which 
distinguishes the imagoes of this group from the usual type is that the dark 
scales appear on the outer edges of the white streaks and fasciae; if a margin is 
present on an inner edge, it is much less pronounced. 

The wide geographical range and the large number of species would lead to 
the inference that the genus is an old one. If so, we would expect to find some 
species which have halted at an early stage in their evolution and have therefore 
preserved a color pattern which should bear some resemblance to the primitive 
one and hence afford a clue to it. Others would have advanced farther, develop- 
ment ceasing at different levels, so that the numerous differentiations produced 
should constitute a chain of related species, broken no doubt by numerous gaps 
but still sufficiently complete to indicate the different directions which evolution 
has taken. The problem of this research is, then, to determine what is the primi- 
tive color pattern of this group and knowing it to trace the paths along which 
evolution has proceeded in the production of the respective patterns of the 
numerous species now in existence. It is scarcely probable that the primitive 
pattern is preserved among any of the earlier genera from which Lithocolletis 
is descended. Such a long period of time has elapsed since the origin of Litho- 
colletis that the species now belonging to ancestral genera have probably deviated 
widely from the type of marking then characteristic of them. This view is 
rendered more plausible by the fact that the subgenus Cremastohombycia, which 
possesses structural generic characters which suggest it as the immediate ancestor 
of Lithocolletis, has a type of marking differing considerably from that common 
to the large and widely distributed typical group and resembling, to a marked 
degree, the type of marking characteristic of some of the species of the smaller 
and seemingly younger group, usually known as the '^flat-larval group. '^ If 
so, we should search for the primitive color pattern among the less differentiated 
species of the typical group of Lithocolletis. 

If evolution takes place in several definite directions irrespective of utility, 
as contended by Eimer, this group should offer an opportunity of testing this 
theory, within certain limits, since many of the highly specialized differentia- 
tions, indicating a high phylogenetic development and requiring a long time to 
perfect, are of almost microscopic proportions and of no conceivable value in 
the life of the organism. Hence it is improbable that natural selection would 
have stepped in to mar any results which might have been produced through 
orthogenesis. 

In a genus such as this, where the color combinations are relatively simple 
and the limits of the marks clearly defined and the pigmental colors belong to 
the single series of yellows (or reddish yellows), browns and blacks, the problem 
of tracing their differentiation both ontogenetically and phylogenetically should 
be one less complicated than in higher groups, and the observations should 
offer more direct testimony as to the means by which such results are obtained. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 109 

(6). Color Classes represented and Structure of Scales. 

Tower (/06) has given a comprehensive survey of the hterature deahng with 
the production of color in insects. Merely a brief summary of the salient facts 
bearing on the subject of this research is given below, and the reader is referred 
to the researches of Tower and earlier investigators for a complete statement 
of what has been accomplished along this line. This author has divided the 
colors of insects into three main classes, based upon their means of production. 
These are chemical or pigmental, physical or structural and chemico-physical 
or combination colors. Pigmental colors are further subdivided into three 
groups: cuticula or dermal, hypodermal and subhypodermal colors. The 
pigments through whose agency colors in the scales of Lepidoptera are produced 
are largely hypodermal; though there is a possibility that certain browns and 
blacks, which are very permanent under the influence of reagents, are cuticula 
colors and therefore located in the walls of the scales, instead of being present 
as granules within the scales. White is probably the only purely physical color 
in insects, although various other colors may be produced through the agency 
of physical causes acting in combination with pigments. The latter, the chemico- 
physical colors, are the most widely distributed and are due to the action of 
light falling upon a surface of different structural modifications over a layer of 
pigment. The various lustrous, metallic and iridescent colors of scales of Lepi- 
doptera are due to this cause. 

In the group under consideration, the lustrous white of the streaks and fasciae 
is produced entirely through structural agencies. The scales over these areas, 
when tested by the addition of alcohol, cedar oil or other similar reagents — a 
method originated by Dimmock ('83), — are rendered transparent and colorless, 
proving that these scales are hollow and contain no pigment. The shining 
golden yellows, browns, black and iridescent blues are combination colors. When 
viewed by transmitted light, the scales reflecting the first three of these colors 
remain essentially the same color; the iridescent blue scales appear to contain 
a pale brown pigment; hence the blue is entirely due to physical causes. 

The scales in the majority of the species have a remarkably uniform struc- 
ture and shape, although showing great variation in size and in the proportion 
of length to breadth. In any one of the typical species, L. lucidicostella or 
cratcegella for example, the scales are wedge-shaped, tapering more or less rapidly 
to the short stem by which they are inserted into the wing. The outer edge of 
the scale is dentate, the number of teeth varying from two or three in the elon- 
gate scales around the apex of the wing in the cilia to seven or eight in the broader 
and shorter scales lying over the wing membrane. In some of the scales, the 
teeth are approximately equal; in others, they are of uneven sizes, and a small 
tooth is sometimes inserted between two larger ones. Variations in the shape 
of scales over the main part of the wing are illustrated by Fig. 4- The last 
row of scales projecting from the apex of the wing over the cilia is composed of 




no EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

exceedingly elongate, linear scales, so that toward their bases they appear 
almost as fine as the ciha themselves. Such a scale, one of the blue iridescent 
scales in the cilia of L. cratcegella, is illustrated by Fig. 5. The scales forming 

the apical spot, a characteristic of a considerable group 
^_^ ^ '^ of species, are smaller than the average and proportion- 

ately broader and are of almost uniform size. The scales 
in the black patch before the apex of such species as L. 
cratcegella are very similar to these. 

All of the scales just described are marked with a 
Fig. 4. Wing scales. serics of nearly parallel strise, there being six or eight 
such ridges extending into each tooth. 
In a few species, which for additional reasons to be adduced later are to be 
regarded as among the farthest advanced phylogenetically, a peculiar highly 
specialized type of scale has developed. The 
extremel}^ brilliant luster of the white mark- 
ings of L. morrisella and ostensackenella and t^ r a • , • 

^ . -TIG. 5. Apical wmg scale. 

P. desmodiella and of the bronzy purple me- 

taUic reflections on the thorax and base of the wings of P. desmodiella is pro- 
duced by these scales. These white scales, one of which is illustrated by Fig. 
6, are broader than the usual type, and the sides curve outward from the base. 
The outer edge of the scale, instead of being coarsely and acutely dentate as in 
the ordinary scales, is obtusely dentate or, sometimes, the teeth 
are entirely absent. The edge then appears scalloped, in a man- 
ner similar to the edge of a pec ten. The depressions between 
the strise, which appear rather broader and more widely sepa- 
T. . ...... • ^^^^^ ^^^^ usual, are concave. The concavities between these 

Fig. 6. White wmg ^ . . „ „ ^ , ^ . 

scale oiL. morrisella. strisB appear as it tormcd by a slopmg out of the sides of the 
strise. The assumption of a concave surface will explain the 
brilliant and slightly opalescent luster of these scales; the various colors being 
produced by essentially the same processes as they are in a soap film. These 
scales contain no pigment whatever; the effects observed are due entirely to 
the effect of light passing through a medium of varying thickness. It may be 
noted here that in L. rohiniella, a species very closely related to L. morrisella, 
this differentiation has not reached the same degree of perfection. The white 
scales are, however, broader and with fewer strise than those of the more typical 
species. The metahic purple scales of the base of the wings and thorax of P. 
desmodiella are very similar to the white scales structurally but differ in that 
they contain a brownish pigment. Their metafile iridescence may undoubtedly 
be ascribed to the same agencies. 

(c) Comparative Study of the Adult Markings. 
The following study of the adult markings was instituted for the purpose 
of discovering whether, as was suggested earfier in the paper, the primitive 




EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. Ill 

color pattern of the genus^ or an approach to it^ still exists among the modern 
species. The presence, in several species, of a number of almost straight or 
slightly modified transverse bands, separated from one another by unpigmented 
fascise, suggested the possibility that such a transversely banded arrangement 
of pigment areas, alternating with unpigmented fascise, was the primitive color 
pattern of the genus. This idea received some support from the fact that in 
L. tiliacella, whose pattern will be described in detail below, the bands in the 
apex of the wing are uniformly pale yellow, with no trace of darker scales. Bear- 
ing in mind the generally accepted fact that, phylogenetically, pale yellow is 
one of the oldest pigmental colors, some portions of the wing of L. tiliacella are 
probably still in the ancestral condition. In this species, seven distinct color 
areas can be made out, most of which are completely separated from one another 
by white (unpigmented) areas which lie over the origins or the tips of the nervures. 
As no species has been found to have a greater number of separate pigmented 
areas, and most of those which do not show a banded type of marking have 
fewer such areas, the conclusion was reached from the study of the adult markings 
thsit the primitive color pattern consists of a series of seven transverse bands, separated 
from one another hy unpigmented areas. 

The verification of this conclusion rests upon the studies of pupal develop- 
ment of the color pattern, which have also shown how the modifications in the 
color pattern, characterizing the different groups described below, have been 
brought about. 

The evidence for the above conclusion as to the primitive color pattern, in 
so far as it is based upon adult characters, is given below. In this relatively 
brief survey of the adult markings of the numerous species comprising the genus 
Lithocolletis and its subgenera, the writer has been guided in the grouping of the 
species, as far as practicable at this stage of the presentation of the results of the 
research, by affinities determined through the discovery of the action of certain 
definite laws in bringing about changes in the shape and extent of the color 
areas. Occasionally, it has been found convenient to bring in arbitrary dis- 
tinctions, used to separate the species systematically. This is true in the second 
group of species discussed; here the presence of a median fascia, while doubtless 
a character valuable to the taxonomist, is in no way an indication that the species 
are closely related to one another. Evolution has proceeded along the same 
line in the different species in respect to this one characteristic alone; the differ- 
entiation of the other markings has been brought about in such different ways 
as to indicate the early branching of this stem of the phylogenetic tree. 

In the discussion of the individual species, the characters referred to are 
those developed through the action of general evolutionary tendencies. The 
various levels which such development has reached before coming to a standstill, 
mark the points where the different subgroups of species diverge from the main 
stems. Within these subgroups, there have been numerous differentiations, 
producing the actual species we now know. Such specific differences must be 



112 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

minor ones, since the general plan of coloration has been already determined. 
Where a group of species has branched early from the main stem, the individual 
species within it will be found to be less closely related; the longer period of 
time allowed for differentiation within the group has given opportunity for 
greater divergence of the individuals composing it. 

In general, no effort has been made to discuss the minute characters separ- 
ating the species. Such characters and their processes of differentiation are 
more properly discussed later. 

Leaving out of consideration for the present the species of the subgenera 
Porphyrosela and Cremastohomhycia, the main branch of the genus may be 
divided, as has been mentioned earlier in this paper, into two natural divisions, 
sufficiently distinguished from one another by the type of larva and by the 
position with respect to the white fascise and streaks of the dark scales bordering 
them. 

In the division whose larva in the later stages is of the normal cylindrical 
type, when a dark margin occurs on but one side of a white mark, it is present on 
the internal edge. In the majority of the species, this margin is the only one 
present; in some species, however, external margins have developed adjacent to 
some or all of the streaks. The external margin is, as a rule, considerably paler 
and less complete than the internal one; in a few cases, where both are equall}^ 
well developed, other characteristics will leave no doubt of the division to which 
any species belongs. For convenience of reference, this division has been 
designated Division I. The species are illustrated on Plate III. 

Several well-defined groups are recognizable. Some of these include a 
considerable number of species, showing close intergradations and indicating 
their origin from a common ancestor at a no very remote period. Other species 
seem to stand apart, showing no very clear affinities with any of the existing 
species. 

One group, comprising L. tiliacella (Fig. 1, PL III; Text Fig. 7), oregonensis,^ 
affinis,^ tritcenianella (Fig. 5), ostensackenella (Fig. 7) and mariceella (Fig. 8) as 

typical forms, and fragilella (Fig. 3) and celtifoliella 
Band I ^' ,. ^^[ ''' J, y\ viL (Fig. 4) as cxtremc deviations from the typical, is char- 
acterized by the presence of at least two complete white 

_^ ,g transverse fascise, the first crossing the wing at about 

^ - -^ . , /' f. „ the basal fourth, the second near the middle. 

Fig. 7. Forewmg of L. lihacella. . . ^ 

In tiliacella (Fig. 7), the ground color is a very pale 
golden; a spot at the base of the dorsal margin is white; the two fascise are almost 
straight, the first but faintly dark margined. At three-fourths of the wing length, 
there are two white dark-margined spots, corresponding in position to a third fas- 
cia, very narrowly separated by pale golden scales which unite with a pale band 
of the ground color beyond. Then follows a fourth white fascia, separated from 
the apex of the wing by a few pale golden scales which mark the position of a band 

1 It was impossible to obtain figures of L. oregonensis, affinis, occitanica and alni. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 113 

of the ground color. Sometimes the apex of the wing is pure white; sometimes 
the extreme tip has a few golden scales. There are thus six white spots (four 
of these are the extremities of fasciae) along the dorsal margin and five on the 
costal margin, separated from one another by ground color. These correspond 
in position with the points of origin or with the tips of the nervures. The 
positions of the white spots with respect to the nervures are as follows: the 
white streak at the base extends somewhat obhquely, lying over the point of 
origin of the tubular part of the upper median vein; the first fascia lies proximally 
over the tip of vein 12, distally over the origin of the tubular part of the upper 
median vein; the second fascia on the dorsal margin lies over the tip of vein 16; 
the pair of white spots at three-fourths lie over the tips of veins 10 and 2 respec- 
tively; the white fascia beyond, over 9 and 5; the last white fascia Hes over vein 7 
on the costa. These white unpigmented areas are the interspaces between 
bands of ground color, seven in number, of which the first two are united on 
the costa. 

In L. oregonensis, the same number of white interspaces are present with 
the exception of the white spot at the base of the dorsum, but the fasciae are 
more bent. The ground color is a deeper golden, and, whereas in tiliacella the 
fasciae beyond vein 10 are represented by a few pale yellow scales only, the 
ground color is distinct, and the fourth fascia is black margined. The extreme 
apex of the wing, which in tiliacella showed only a faint tinge of golden, contains 
a black apical spot. In affinis, tritcenianella (Fig. 5), ostensackenella (Fig. 7) 
and mariceella (Fig. 8) there is a reduction in the number of white fasciae 
and spots; the spots over veins 9 and 5 are wanting, and the ground color 
extends uninterruptedly from vein 10 to vein 7, In ostensackenella, the white 
streak enclosing the apex has become divided into a pair of opposite spots; the 
base of the wing is dark brown. In affinis and tritcenianella, the white streak 
before the apex does not extend entirely across the wing. In tritcenianella, the 
first white fascia is situated before the tip of vein 12. As it occupies the same 
position with respect to the origin of the upper median vein as the corresponding 
fascia in tiliacella {Fig. 7), it would seem that the origin of this vein is the 
factor determining the position of the first fascia. This conclusion is cor- 
roborated by identical observations on other species. 

L. fragilella (Fig. 3) and L. celtifoliella (Fig. 4) are not closely related 
to the preceding members nor to one another. In both, the fasciae are 
densely dusted internally with dark-tipped scales; in fragilella, the fasciae are 
suffused with pale yellow; in celtifoliella, the fasciae are acutely angled, and the 
oblique costal and dorsal arms reach the margins proximal to their usual position. 
As will be seen later, this displacement of the extremities of the first two fasciae 
proximally is of common occurrence and has been one of the principal forces in 
the evolution of the species of this genus. 

Desmodiella (Fig. 9), the single representative of the subgenus Porphy- 
rosela, which structurally is in advance of Lithocolletis, has retained the banded 



114 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

type of marking. There are two lustrous white fasciae, dark margined on both 
sides, on a dark reddish brown ground color, showing a deep purple metaUic 
luster at the base of the wing. 

In another group of species, the median fascia only has been preserved, 
either in its primitive almost straight condition or has become angulated. Most 
of the species bear no close relationship to one another, and it would seem, there- 
fore, that the group is merely an artificial one and that the characteristic of a 
median fascia is one which appears in several divergent lines of development. 
The species which may be included in this group for purposes of discussion are 
the following: L. morrisella (Fig. 48), uhlerella (Fig. 49), lucetiella (Fig. 51), 
symphoricarpella (Fig. 54), gemmea (Fig. 53), martiella (Fig. 52), celtisella (Fig. 
56) and apicinigreUa (Figs. 55a, 556). Rohiniella (Fig. 50) shows a very clear 
natural relationship with the first two mentioned species, and differs from them 
only by the separation of the median fascia into a pair of opposite costal and 
dorsal streaks,^ and the obliteration of the first dorsal streak by dark scales. 

Morrisella (Fig. 48,), uhlerella (Fig. 49) and rohiniella (Fig. 50) are a 
remarkably homogeneous triad of species; the figures will suffice to give a clear 
idea of their characteristics. In lucetiella (Fig. 51), the entire basal half of the 
wing is white, with the exception of a longitudinal streak from the base follow- 
ing the course of the upper median vein; the apical half of the wing closely 
resembles that of tiliacella (Fig. 7). In symphoricarpella (Fig. 54), the basal 
half of the wing is of the golden brown ground color; the white streaks over 
veins 9 and 5 are lacking. In martiella (Fig. 52) and gemmea (Fig. 53), there 
is a white basal streak;^ in gemmea a white spot on the dorsal margin occupies 
a position nearly corresponding to the extremity of the first fascia. In these 
two species, as in morrisella. uhlerella and rohiniella, a group of small scales in 
the apex forms the black apical dot. Celtisella (Fig. 56) and apicinigreUa (Figs. 
55a, 556) are characterized by the presence of an acutely angled fascia and a 
median white basal streak. In celtisella, the dorsal margin is also white from 
the base to the fascia. ApicinigreUa is an extremely variable species; sometimes 
the fascia is broken in the middle; an extreme aberrational form is represented 
by Fig. 556. 

Basistrigella (Fig. 57), although a somewhat isolated species, is perhaps 
most closely related to celtisella (Fig. 56) and apicinigreUa (Figs, b^a, 556) of 
the above group. The median pair of streaks are of equal width throughout 
and each is extended at its extremity along the margin to the base. 

Bataviella (Fig. 58) stands entirely apart from any of the species of 
the American fauna; there are, however, several closely related species in the 
European fauna. The white spot which was present at the base of the dorsal 
margin in tiliacella and did not reach the costa, is here often extended entirely 

1 The terms '^ costal streak" and '^ dorsal streak" are used to designate the white and usually 
triangular spots situated on the costa and dorsum respectively. 

2 The ''basal streak" is the white longitudinal hne beginning at the base of the dorsum and 
extending along the middle of the wing for about one-third its length. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 115 

across the wing thus separating a basal patch of dark scales from the band of 
similar scales beyond it. In this species^ therefore^ the number of distinct 
patches or bands distinguishable along the costa is seven^ separated more or 
less completely from one another by white interspaces. 

The remainder of the species^ and by far the most numerous^ have been 
included in one large group^ because all can be traced to a common origin and 
all are manifestations of a similar tendency in development. All are charac- 
terized by the presence of pairs of opposite curved, oblique costal and dorsal 
streaks, widest on the margins and tapering in the middle of the wing to pointed 
apices. There are a number of well-defined subgroups, due to the halting of 
individuals at different stages in the general process of evolution and the differ- 
entiation of a number of species from each of these. 

Standing at the foot of the group and somewhat apart from the other 
species, is auronitens (Fig. 10). In it, there are three dorsal streaks before the 
tornus,^ but little oblique and not displaced proximally from their normal position 
with respect to the nervures. 

Argentinotella (Fig. 11), occitanica and leucothorax (Fig. 13) are also 
characterized by the presence of three streaks on the dorsum before the 
tornus. These are decidedly oblique, especially in leucothorax, in which there 
is also a well-defined apical spot. In occitanica, the first, fourth and fifth costal 
streaks present in argentinotella are wanting. 

In fitchella (Fig. 14), there are but two dorsal streaks before the tornus; 
the first is unusually large, suggesting from its position the possibihty of its 
formation from two white streaks. That this has occurred and the processes 
bringing it about wih be discussed later. 

Salicifoliella (Fig. 15) and tremuloidiella (Fig. 16) are not closely related to 
any of the large subgroup of species soon to be discussed. These two isolated 
species are the result of differentiation and advancement along other lines, when 
there has been a cessation, at a lower level, of the common course of evolution, 
which if continued, culminates in such forms as hageni (Fig. 17) and later, in 
the large subgroup of species of which cratcegella (Fig. 36) and obscuricostella 
(Fig. 25) are typical representatives. Because of this, their markings will be 
better understood when the laws governing their transformation have become 
apparent. 

Insignis (Fig. 20), hageni (Fig. 17) and arbutusella (Fig. 18) are properly 
grouped together. In another variety of insignis, the white extends from the 
basal streak across the wing to the dorsum, forming a quadrate white patch similar 
to that of hageni. These three species are likewise differentiations from an offshoot 
of the main stem, although at a higher level than the two preceding species. 

We now come to the large subgroup of species characterized by two oblique 

1 The three margins of the wing are the costa or upper margin, the termen or outer margin 
and the dorsum or inner margin. The junction of the costa and termen is the apex of the wing; 
the junction of the termen and dorsum is the tornus. In this group, where there is no defined 
termen, the tornus is the place where the hue of scales in the ciha meets the dorsal margin. 



116 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

streaks on the dorsum, the first usually very oblique, the second, which is placed 
at the tornus, often nearly perpendicular, and four costal streaks (rarely five as 
in populiella and rileyella). These are popuUella (Fig. 27), diaphanella (Fig. 28), 
salicivorella (Fig. 29), deceptusella (Fig. 30), alnicolella (Fig. 32), alni, incanella 
(Fig. 34), scudderella (Fig. 35), ledella (Fig. 33), malimalifoUeUa (Fig. 37), cratce- 
gella (Fig. 36) and propinquinella (Fig. 38), in which the black scales in the apex 
are not massed to form a circular apical dot; and carycealhella (Fig. 21), rileyella 
(Fig. 22), ostrycefoliella (Fig. 23), olivceformis (Fig. 24), ohscuricostella (Fig. 25), 
kearfottella (Fig. 26), obsoleta (Fig. 41), sexnotella (Fig. 39) and ceriferella (Fig. 
40), in which a number of small black scales in the apex are grouped into an 
almost circular, definitely outlined, apical spot. In obsoleta (Fig. 41), this spot 
is very ill-defined, as are all the other markings. With the exception of the 
three last mentioned species, a white median basal streak extends to about one- 
third of the wing length. This streak may be margined above and sometimes 
around its tip with dark scales. In some of the species, there is, on the dorsal 
margin, a small white spot, often extended almost to the base of the wing and 
with its outer edge about midway between the base of the wing and the first 
dorsal streak. In a few cases (e. g., incanella (Fig. 34)), this spot is indistinctly 
margined on its inner side by a short oblique line of darker scales. In obsoleta 
(Fig. 41), sexnotella (Fig. 39) and ceriferella (Fig. 40), the entire basal portion 
of the wing is without markings, the ground color extending uniformly over it. 

Lastly, there is that subgroup of species in which there is but one margined 
dorsal streak and that one is situated at the tornus; the basal portion of the 
wing is, to a great extent, shining white, and any colored markings present are 
longitudinal. These are trinotella (Fig. 47), quercialbella (Fig. 46), clemensella 
(Fig. 45), lucidico Stella (Fig. 44) and argentifimbriella (Fig. 43). Phylogenetically 
considered, albanotella (Fig. 42) should be included here, as representing an earlier 
stage in the process resulting in the production of these five species. In this 
species, a first dorsal streak is defined by an incomplete margin not reaching the 
dorsum. 

In Division II of the genus, illustrated on Plate IV, where the modified flat type 
of larva persists through six larval instars, the chief aggregation of dark scales is 
on the outer side of the white streaks and fasciae. Where an additional margin 
occurs on the inner side of the white markings, the outer one has broadened con- 
siderably and is often prolonged at the angle of a fascia as a dense aggregation of 
dark tipped scales. There seems to be less tendency in this group toward the con- 
centration of dark scales in the apex over a definitely outlined area ; the tendency 
is rather for all the scales to become dark tipped, producing an evenly dusted 
effect. As in Division I, several groups of species are recognizable. 

In one group, there is a tendency to preserve, either straight or angulated, 
two white fasciae, the first crossing the wing at the basal fourth, the second at 
the middle. In obstrictella (Fig. 64), these fascise are almost perpendicular 
and straight; the pair of white streaks beyond often form a third fascia. In 



EVOLUTION OF COLOE PATTERN IN LITHOCOLLETIS. 117 

tubiferella (Fig. 65), aceriella (Fig. 66) and hamameliella (Fig. 67), these 
fasciae are straight and but httle obUque. In tubiferella (Fig. 65), they are the 
only white markings, except sometimes a very small white dot near the apex. 
In aceriella (Fig. 66) and hamameliella (Fig. 67), there are, in addition, an 
obhque white streak at the base of the dorsum, a longer obhque dorsal streak at 
the tornus and a small white streak opposite it on the costa. Ostryarella (Fig. 
6S) , corylisella (Fig. 69), CBSculisella (Fig. 70) and guttifinitella (Fig. 71) constitute 
a closely related series, separated from one another by small differentiations. 
In these species, the two fascise are bent outwardly below the costa, scarcely 
enough to be called angulated. In guttifinitella, the pale streak at the base of 
the dorsum is almost or sometimes entirely wanting. In lentella (Fig. 73) and 
carymjoliella (Fig. 72), the fascise are distinctly angulated. 

In cincinnatiella (Fig. 75), macrocarpella (Fig. 74), saccharella (Fig. 76), 
hamadryadella (Fig. 77), umbellularice (Fig. 78) and agrifoliella (Fig. 79), at least 
one of the two white fascise has become acutely angulated. In hamadryadella 
(Fig. 77) and umbellularice (Fig. 78) , the white fascia at the base is preserved to the 
costa, although in umbellularice, it is almost separated into two parts. In agrifoliella 
(Fig. 79), the position of this fascia is indicated by two patches of dark scales which 
would form its external margin. In hamadryadella (Fig. 77), very complete 
internal margins to the white fascise have developed; the ground color has, 
however, shrunk away toward the base, so that the line of dark scales extends 
through the middle of a broad white band. In cincinnatiella (Fig. 75) and 
macrocarpella (Fig. 74), the two fascise are uniformly angulated; the white patch 
at the base does not reach the costa. The costal arm of the first fascia of 
saccharella (Fig. 76) is wanting, its dorsal arm is very obhque and confluent with 
the oblique basal streak. 

A group of species compiking fl.etcherella (Fig. 80), arcuella (Fig. 81), betuli- 
vora (Fig. 82), australisella (Fig. 83), bethunella (Fig. 84), chamber sella (Fig. Sb), 
-cervina (Fig. 86), platanoidiella (Fig. 87), castaneceella (Fig. 88) said fasciella (Fig. 
89) retains but the single median fascia, sometimes almost divided at its angle. 
A pair of opposite oblique streaks represent the former complete fascia at the 
basal fourth of the wing in the five first mentioned species of this group; in the 
remaining five, the costal streak only is present. In castaneceella (Fig. 88) and 
fasciella (Fig. 89), there has been an extensive progressive diminution in the white 
markings; the median fascia is the only white marking remaining in fasciella. 

In gaultheriella (Fig. 91) and nemoris (Fig. 90), there is no median fascia; 
instead of it a pair of costal and dorsal streaks. In nemoris, the first pair of 
streaks meet, forming a fascia; in gaultheriella, they are separate. 

Lastly, there is that group of four species, in which a white longitudinal 
streak extends from the base along the dorsal margin, reaching to or beyond the 
middle. These are mediodorsella (Fig. 92), quercivorella (Fig. 93), ulmella (Fig. 
95) and conglomeratella (Fig. 94). In the two former, this streak stops abruptly 
at the middle of the dorsal margin; in mediodorsella (Fig. 92), it connects with 



118 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

the dorsal arm of an angulated fascia. In ulmella (Fig. 95) and conglomeratella 
(Fig. 94), the white streak extends almost to the tornus, where it connects with 
a dorsal streak running obliquely into the apex. 

A rather noteworthy feature common to both divisions of the genus is this : 
the third white fascia or the third pair of streaks, whose extremities are placed 
over the tips of veins 2 and 10, are never displaced from their normal position, 
and only in rare instances are they much oblique. These instances are almost 
entirely confined to Division 11. In such case, the impression of length and 
obliquity is gained through the fact that the more apical portion of this streak 
is homologous with the white streak over vein 5. The greatest changes have 
taken place in the positions of the first two pair of streaks, resulting in their 
displacement toward the base. 

In either of the two divisions of the genus, the greatest number of more or 
less distinct bands of ground color has been seven. The first of these crosses the 
base of the wing and is usually confluent with the second in the costal half of 
the wing. The position of the white unpigmented areas separating these bands 
of ground color appears to be determined by the points of origin or by the tips 
of the longitudinal nervures. The question to be decided is whether such a 
banded arrangement of pigment areas represents the primitive type of colora- 
tion, and if so, how has evolution acted in bringing into existence the present 
great complex of species. 

A group of species (Figs. 59a, 596, 60, 61, 62, 63) more primitive in 
generic structure, namely, Cremastobomhycia, shows a type of coloration strik- 
ingly similar to that of some of the species of the ^^flat-larval group." An 
examination of this group discloses the fact that nowhere are there more than 
four costal white streaks as compared with five or six in some of the species 
of the more recent branches of the genus. Apparently, then, because of the 
fewer separate bands of ground color present in species of this group, the primitive 
type of marking is not to be sought for among the species of the ancestral group. 

The observations that have been made point to the conclusion that the 
primitive type of coloration is made up of seven distinct transverse bands. The 
results of the investigations upon the development of color in the pupal wings, 
now to be presented, confirm this view and, in addition, furnish evidence of the 
means by which transformation of the bands into the various types of color 
pattern has been accomplished. 

(d) Ontogenetic Development of the Color Pattern. 

1. Historical. 
Tower ('06) has summarized the general results of researches upon the de- 
velopment of colors in pupal wings as follows : 

^^The studies upon the origin of color in the wings of Lepidoptera have 
shown that there is a regular order of development, not only of colors but also 
of the areas in which spots and stripes appear. The wings, which are colorless 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 119 

at first, become opaque, yellowish or light drab, beginning first near the base of 
the wing and spreading distalward. Soon spots, stripes and adult markings 
appear, at first proximad, then more and more distad, then between the nervules 
and, last of all, upon the nervules. First, the purely pigmental or chemical 
colors develop, and these are followed by the chemico-physical.'^ 

The principal researches have been those by Schaffer (^89), Van Bemmelen 
('89), Urech ('91), Haase ('93), Mayer ('96) and most recently by von Linden 
('98, '02). The principal work of the first three authors was upon Vanessa and 
Pyrameis. Van Bemmelen ('89) has shown that the first color to appear in 
Pyrameis cardid is a pale brownish yellow which deepens to the reddish brown 
ground color; upon this ground color, the black spots appear. The development 
of the color in Vanessa urticce follows very much the same sequence, as pointed 
out by both Van Bemmelen and Urech. Urech ('91) has shown that in Vanessa 
10, the adult spots and colors appear directly upon the primitive white of the 
pupal wing; that is, the yellow appears over a restricted area of the wing; 
following this, a reddish tinge appears, which, over another portion of the wing, 
gradually deepens to the reddish brown ground color. Later, the adult black 
spots develop directly upon the primitive white wing; some at least of the white 
spots of the adult represent the primitive white of the pupal wing. In Van 
Bemmelen's opinion, a considerable amount of modification takes place in the 
wings after the first appearance of color, so that the adult design may differ 
considerably from that first laid down. Urech's ('91) view is directly opposed 
to this; according to him, the different color areas are definitely laid down from 
the beginning and are therefore older phylogenetically than the particular colors 
of the adult wing. He therefore regards color as the important factor in deter- 
mining phylogenetic position— ''die Farbe ist das Primare, die Zeichnung das 
Secundare." 

Haase ('93) worked upon several species of Papilio and found that the 
wings are transparent or colorless, later becoming whitish; this white then gives 
way to a yellowish ground color upon which the adult colors begin to appear, 
undergoing considerable development before reaching their definitive adult 
condition. 

Mayer ('96) traces the development of the scales from modified hypodermis 
cells, the ''formative cells of the scales," from their first appearance as blunt 
outgrowths from these cehs until they are fully formed and pigmented. In 
addition to confirming the conclusions of previous investigators as to the sequence 
in the appearance of colors, Mayer has shown that "the transparent condition 
of the wings corresponds to the period before the scales are formed and to the 
time when they are still completely fuh of protoplasm. The white condition is 
caused by the withdrawal of the protoplasm from the scales, leaving them as 
little hollow bags filled with air. In this condition, they diffract the light and 
appear pure white. 

"After the protoplasm has completely withdrawn from the scales, the 



120 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

'blood' or hsemolymph of the pupa enters them; and soon after this, the wing 
becomes of a uniform dull yellow or light drab color. This color is due to the 
fact that soon after the hsemolymph has entered the scales, it changes to a dull 
ochre-yellow and finally to a drab color. The same change takes place in hsemo- 
lymph which has been removed from the pupa and exposed to the air. The 
mature colors are clue to chemical changes in the hsemolymph itself. They 
first appear in places between the nervures, never upon the nervures themselves. 
The last places to acquire the mature coloration are the outer and costal edges 
of the wings and the nervures. . . . 

''Dull ochre-yellow and drabs are, phylogenetically speaking, the oldest 
pigmental colors in the Lepidoptera, for these are the colors that are assumed by 
the haemolymph upon mere exposure to air. The more brilhant pigmental colors, 
such as bright yellows, reds, greens, etc., are derived by more complex chemical 
processes. We find that dull ochre-yellows and drabs are at the present day the 
prevalent colors among the less differentiated nocturnal moths. The diurnal 
forms of Lepidoptera have almost a monopoly of the brilhant colorations, but 
even in these diurnal forms, one finds that duh yehow or drab colors are stih 
quite common upon those parts of their wings that are hidden from view.'' 

The most recent researches upon the subject of development of color in 
the pupal wings of Lepidoptera are those of von Linden ('98, '02). The results 
of her investigations are embodied in two papers, the first being practically in- 
cluded in the second. Her observations lead to the conclusion that the adult 
color pattern develops from a number of separate transverse bands which dispose 
themselves upon a uniform ground color in a manner characteristic of each 
species. A distinction is thus made between ground color and that forming the 
color pattern. These transverse bands (longitudinal according to Elmer's view) 
occupy definite positions upon the wing determined by the course of the nervures 
and trachese. This is the condition found among Papilios, Vanessas, Sphingids, 
the higher Bombycids and even among some of the Geometrids. These larger 
bands are formed by the broadening out and fusion of narrower bands ("bande- 
lettes primaires") preserved only among more primitive forms. On the one 
hand, the bands may fuse to form a uniform color; on the other, they may break 
up into a series of spots, which become smaller as the ground color encroaches 
upon them. The hindwing is arrested at a point less advanced than the fore- 
wing; this, combined with the greater tendency toward fusion of the bands 
which is in fact due to the modified form of the hindwing, creates the erroneous 
impression that the hindwing is more advanced than the forewing. 

The author claims that her results support the laws which Eimer has promul- 
gated for species differentiation based upon a study of adult coloration : 

"/Z est done evident que les his que Eimer a trouvees en etudiant la phylogenese 
du dessin des Lepidopteres peuvent etre admises point pour point pour Vontogenese. 

"Mes reserches preuvent done que le dessin des Papihons ne parait pas 
soudainement, . . . que les phases que ce dessin parcourt pendant son developpe- 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 121 

ment ontogenetique, sont analogues aux phases que le dessin de Tespece du 
Papillon a dti parcourir pendant son developpement phylogenetique, que le loi 
qui gouverne la biogenese est aussi confirmee par ce procede, qui s'accomplit 
pendant la metamorphose de Tinsecte^ et qu'en fin les theories de Eimer sont 
solidement fondees, quand il dit que chaque animal ne pent varier que dans peu 
de directions determinees par les influences du dehors et par sa propre consti- 
tution, et que Fespece se forme par genepistase/^ 

Recapitulation is, however, only partial and confined to primitive forms: 
^^Les phenomenes de la phylogenese se produisent le plus clairement dans 
le developpement du dessin chez les formes les plus primitives. Chez les groupes 
les plus advances, ces phenomenes sont masques par ^intervention dela tachy- 
genese qui montre sa plus grande influence dans le developpement des ailes 
inferieures.'' 

With regard to the succession of colors upon the wing, the same author 
finds that it is only in the primitive forms that the scales forming the dark mark- 
ings pass through the intermediate shades of yellow to reach their final gray or 
black condition; in the higher forms, they remain uncolored until the scales 
forming the ground color reach their full development, later passing directly 
from the colorless stage into gray or black. The color appears first at the tip 
of the scales, spreading gradually to the base. Scales which are destined to 
acquire their pigment later are not fully formed when the scales of the ground 
color attain the adult form and color. Therefore, color may be taken as a 
measure of the degree of development of a scale. 

2. Methods. 

In the study of the development of color in the wings of Lithocolletis , speci- 
mens of the summer generations were used for observation. No overwintering 
pupse have been observed. In the summer generations, the average duration 
of the pupal state is about a week; it may be as short as four or five days. 

The chrysalids were removed from the mines shortly after pupation and 
kept under careful observation. For some time, no change in the brown color 
of the pupa is to be observed, then two faintly darker brown spots, corresponding 
in position with the eyes of the imago, become visible through the pupal envelope. 
These spots rapidly turn black, and very shortly after, the wings, which up to 
this time have appeared transparent through their thin chitinous envelope, 
begin to lose their transparency. This marks the beginning of the white stage. 
A day or two later, the yellow colors begin to appear upon the wing. The chief 
difficulty in the study lies in securing a suitable series of these earliest stages, 
as the colors are very faint at this period, and numerous dissections are often 
required before the necessary material can be obtained. In later stages, the 
markings are visible through the pupal envelope, and a choice of specimens can 
be made with relative accuracy. 

The dissections were made in .6 per cent NaCl solution under a simple 



122 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

dissecting microscope of moderate power by means of fine needles set in match- 
sticks. One needle is inserted through the abdomen and held rigid; another 
through the middle of the upper side of the thorax. The second needle is now 
drawn forward, tearing apart the pupal envelope and carrying with it the anterior 
part of the thorax with wings attached. The structure of the pupa with separate 
envelopes for wings and legs in the lower Microlepidoptera renders this method 
of procedure highly successful. The thorax may now be torn apart, allowing 
the wings to float out flat. With a little experience, it is possible to remove 
the wings in this manner without the displacement of either scales or cilia. The 
wings thus removed from the pupa vary in length from L5 to 2 mm., being, 
therefore, about one-half the length of the imaginal wings. 

The wings were examined with a simple lens to determine the general extent 
of the color areas. For the more accurate observation of the positions and limits 
of pigmented areas and individual scales pigmented, I have used a compound 
miscroscope, 16 mm. objective, 4x eyepiece, giving a magnification of 60 diam- 
eters. The observations were made almost entirely by reflected light and 
under a cover glass. In the early stages, where the colors are very faint, I have 
found black paper, as suggested by von Linden, very useful for a background. 
Somewhat later, a pure white background is advantageous in the detection of 
the first appearance of grayish tints. 

All of the wings were examined in .6 per cent NaCl solution, shortly after 
removal from the pupa. Observations made thus are vastly more satisfactory 
than when permanent mounts are employed. A number of the wings were, 
however, transferred to absolute alcohol between pieces of glass to prevent 
curling, and after about an hour embedded in Venetian turpentine made as 
follows : 

Commercial Venice turpentine is mixed in a tall cylinder glass with an 
equal volume of 95 per cent alcohol. The mixture is aflowed to stand in a warm 
place for three or four weeks and then decanted. 

The mounting medium thus prepared is thin enough to flow easily and not 
displace the deUcate cilia. However, the attendant darkening of the colors is a 
disadvantage in comparing with adult specimens. 

I have found it possible to preserve all except the earliest stages without 
the use of a mounting fluid, if the slide containing the wing under a cover glass is 
immersed in absolute alcohol for a short period. Later the cover glass may be 
closely appressed and fastened down around its edges. 

Both forewings in each specimen were examined; the two sets of observa- 
tions thus serving as a check on one another. In the following descriptions, 
reference is made to the forewings only. The hindwings are practically uni- 
colorous, usually paler than the forewings, and reach their final development 
somewhat in advance of the forewings. Their development yields no new 
facts, merely confirming the results of earlier investigators upon the sequence 
of colors. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 123 

3. Observations. 

Two factors were taken into consideration in determining the choice of species 
to be studied, namely, the general type of adult marking and the presence or 
absence of certain characters such as an apical spot or dark marginings adjacent 
to white streaks or fascise. The object of the research is twofold: (1) to deter- 
mine, if possible, the primitive or fundamental color pattern and its mode of 
transformation into the adult pattern and (2) to determine the relative time of 
appearance and manner of development of the various dark markings, the 
characters referred to above. 

The evidence furnished by the development of color in the pupal wings 
taken in conjunction with a comparative study of the adult markings has con- 
vinced me that the primitive color pattern is composed of a series of uniformly 
colored pale yellow ban ds, seven in number, placed transversely on the wing and 
separated from one another by white fasciae (unpigmented areas) (Fig. 8) . These 
bands are typically straight and, with the exception of 

the first, cross the wing almost perpendicular to the mar- j, ^^ ^ v vi 

gms. The bands, when present m their primitive con- ■ ' ' 

dition, have certain defined positions. Their hypothetical 
typical positions are illustrated by Fig. 8. In what fol- '" ^ 

lows, it will be noticed that there is a definite relation _ ^^ ,.,... 

. . Fig. 8. Hypothetical primitive 

01 bands to veins. Band I occupies the extreme base color pattern of the forewing of 
of the wing, beginning at the base of the dorsum and Lithocoiietis. 
broadening on the costa; the white streak which sepa- 
rates it from Band II passes obliquely from the base of the dorsum toward 
the costa, lying over the point of origin of the tubular portion of the lower 
median vein. Band II crosses the wing on the basal side of the tip of vein 
12; the position of the white fascia which separates it from Band III seems 
to be determined rather by the point of origin of the tubular portion of the 
upper median vein than by the tip of vein 12, as this vein often extends con- 
siderably beyond the origin of the upper median vein without causing a cor- 
responding broadening distally of the second band. It sometimes happens 
that vein 12 is unusually short, and then the white fascia lies over its tip and 
over the origin of the upper median vein. On the costa, the inner border of 
Band III hes just beyond the origin of the upper median vein, and on the dorsum, 
the outer border extends almost to the tip of vein 16. Band IV crosses beyond 
the tip of vein 16 and hes over the bases of veins 10 and 2, its outer border being 
just within the tips of veins 10 and 2. Band V on the costa is placed between 
veins 10 and 9, on the termen between veins 2 and 5 and lies over the transverse 
vein. Band VI is placed between veins 9 and 7 on the costa and beyond vein 5 
on the termen. Band VII crosses the apex of the wing. Thus it will be seen 
that the position of the bands is largely determined by the position of the longi- 
tudinal nervures, the tips of the veins marking the extremities of the unpig- 
mented fasciae separating the bands. In no case in the adult has this pattern 



124 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 



been preserved in its original primitive condition as seven distinct transverse 
bands; fusions either partial or entire have taken place between two or more 
adjacent bands. Displacements have also occurred^ due to a shrinking away 
of color from one side of a white interspace and its extension over the white on 
the other side. Finally^ some of the bands may have shrunk away almost 
entirely. 

The following is a list of the species in which the development of the pattern 
has been traced from the first appearance of color to the adult markings : 



Lithocolletis tiliacella Cham. 
Lithocolletis tritcenianella Cham. 



Lithocolletis cratcegella Clem. 
Lithocolletis ostrycefoliella Clem. 
Lithocolletis lucidicostella Clem. 
Lithocolletis morrisella Fitch 
Lithocolletis hamadryadella Clem. 
Lithocolletis hethunella Cham. 
Lithocolletis ulmella Cham. 
Lithocolletis cesculisella Cham. 
Cremastobombycia ignota F. and B. 



Species in which two or more of the bands 
have been preserved almost in their 
primitive condition as respects position 
and shape. 

Species in which changes in shape or 
position or both and more or less com- 
plete fusions of some of the bands have 
taken place and certain differentiations 
and specializations have appeared, such 
as the development of black scales at 
places other than those directly con- 
tiguous to the white interspaces be- 
tween the bands. 



In the following species, the development of the pattern was observed only 
in part for the purpose of comparing the development of certain characters in 
these species with that of similar characters in related species, or with a view of 
determining the relative time of appearance of certain characters: 
Lithocolletis hageni F. and B. 
Lithocolletis robiniella Clem. 
Lithocolletis carycefoliella Clem. 
Cremastobombycia solidaginis F. and B. 

In all of the species studied, the wings are at first transparent and glassy 
in appearance, corresponding to the period, as observed by Mayer (^96), before 
the protoplasm has been retracted from the scales. Following this is the so- 
called white stage, in which the wings appear by reflected light almost pure white 
and by transmitted light pale bullish, due to the hsemolymph contained within 
them. The scales are at this period colorless and transparent, containing only 
air. The white stage lasts from one to two days, giving way to a pale yellow 
over certain defined areas, as the hsemolymph enters the scales and the pigment 
begins to form. This yellow color may be preserved throughout pupal develop- 
ment almost as originally laid down, or it may go through a process of transfor- 
mation before reaching the adult condition. In either event, it gradually deepens 
in tint and constitutes the ground color upon which the dark streaks (margins) 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 125 

and spots are to appear. The development of the pattern takes place very 
rapidly during the last part of the pupal state. The time intervening between 
the first appearance of a tinge of yellow on the wings and the emergence of the 
imago is largely dependent upon temperature and is often less than twenty-four 
hours. Development takes place more rapidly in day time than at night and 
is strikingly retarded during cloudy weather. 

Lithocolletis tiliacella Cham. 

In the first specimen examined, the wings were removed from the pupa at 
a very early stage of development. The yellow color is scarcely differentiated 
from the clear buffish white wing {Fig. 9) . The only bands ^ jtr jy 

which can be distinguished are II, III and IV. Band II 

crosses the wing just before the tip of vein 12, thus occu- ' j 

pying its primitive and typical position. It is the palest 

and least defined of any of the three bands present. Its Fig. 9. Early stage in the 
outer edge is definitely defined, but its inner edge fades d^^^^^P^^^t ^f f^^ ^^ t^e 

^ ^ ^ ^ ^ wmg 01 L. hhaceUa. 

mto the clear basal part of the wing, the color being ex- 
tended farthest toward the base just within the costal and dorsal margins. 
Band III has also preserved its primitive position and form. It is somewhat 
darker than II, but uniformly colored throughout its breadth, the outer edge 
not darkened. Its width is scarcely greater than that of the clear band pre- 
m jv V ceding it. Band IV is the most deeply colored as well 

JI \ I ; VI YU 

^ ' . -' i as the broadest of the three bands; it is of the same 

i ' breadth as in the adult. Even at this early stage it is 

prolonged outwardly almost to the end of the cell. The 

Fig. 10. Later stage in entire apical part of the wing and cilia are of the 

the So^nklr'" " ^^^^^ ^hi^i^h ^^1^^^ ^he^^ '^^i^g ^o indication whatever of 

bands. 
The wing in the next stage examined shows considerable advance over the 
stage just described {Fig. 10). There has been a decided deepening of color, 
and the adult pattern has been laid down, with the possible exception of Bands 
VI and VII, which have not as yet been clearly differentiated as bands although 
there is a faint yellow tinge in a few of the scales in the apical portion of the wing. 
These bands are usually indistinct and sometimes absent even in the adult. 
Band I is united with Band II along the costa; this condition was apparently 
not produced by the independent origin of Band I and its later fusion with II 
but by a uniform and gradual deepening of the wing below the costa. The 
outer edge of Band II is now somewhat bent outward in the middle, and the 
scales in the middle of the outer edge are beginning to deepen in color, thus 
foreshadowing the appearance of the dark margin, but there is as yet no hrown 
pigment in the scales. Band III is also somewhat bent outwardly as in the 
adult, and its dark margin is present on the costa and dorsum only, the costal 
margining being much less distinct than the dorsal; neither extends more than a 



126 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

short distance onto the wing proper. The middle of Band IV is faintly con- 
nected with a pale band beyond, which represents Band V. Its margins have 
reached more nearly their adult condition than any other of the wing markings. 
The margin on the dorsal half is almost as greatly developed as in the adult; 
that on the costal half is represented only by a few black scales. 

The next stage studied shows no further change in the shape or extent of 
an}^ of the bands, the changes which have taken place being confined to continu- 
ation of processes already begun, namely, the deepening of the outer edge of 
Band II, thus forming the internal margin of the first white fascia in the adult, 
the approximation of the costal and dorsal parts of the margin of Band III, so 
that they are now but little separated, and their darkening to the adult color, 
the advance of the margins of Band IV to their adult condition, the deepening 
of Band V so that it now appears quite distinct and as in the adult. 

This is the only species studied which shows any distinction between the 
bands in regard to their relative time of appearance. Bands II, III and IV are 
the first to appear, and in the youngest specimen examined, Band IV was de- 
cidedly in advance of the other two as shown by its deeper color and by its 
extension outwardly in the middle. It is, therefore, probably safe to assume that 
Band IV is in this species, the earliest to appear ontogenetically. As will be 
shown later, L. tiliacella has probably in many respects conserved more closely 
than any other of the now existing species the primitive type of color pattern, 
and hence the sequence observed in the appearance of the bands in the ontogeny 
may also be true for the phylogeny. 

Lithocolletis tritaenianella Cham. 

At the earliest stage at which it is possible to discern any indication of 
marking, five very pale yellow bands are visible upon the wing {Fig. 11). These 

are uniformly colored and straight and are placed trans- 

^^' versely upon the wing, showing no signs of fusion with 

J one another. The first of these is, in fact, I + II, as 

shown by the faintly paler streak extending into it from 

Fig. 11. Early stage in the the basc of the dorsum. The sccond. Band III, occu- 

deveiopment of color in the pj^g j^g ^g^^j positiou, but in this casc the position of 

wing of L. iriioenianella. ,. p. . .^ tx* inij 

the white lascia separating it from II is wholly deter- 
mined by the point of origin of the upper median vein, as vein 12 extends for a con- 
siderable distance into Band III. The third, Band IV, is normal in position and 
shape. That the fourth band is in reality composed of Bands V and VI is shown 
by its origin just beyond the tips of veins 10 and 2 and by its extension distally 
over the tips of 9 and 5 which in the primitive color pattern mark the position 
of the white fascia separating Bands V and VI. Band VII crosses the apex of 
the wing. The white interspaces between Bands II and III and between III 
and IV are of about the same width as in the adult, but that between IV and 
V + VI is considerably wider and shows no indication of the angulation which 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 127 

is present in the adult; that is, Band IV has not yet begun to extend outwardly 
through the cell. The space separating V + VI from VII is at this stage about 
one-half the width of V + VI and extends entirely across the wing, thus differing 
strikingly from the condition found in the adult. 

The development for some time consists merely in a uniform darkening of 
the ground color as first laid down without any change in the extent of the bands. 
At a somewhat later stage, simultaneously with the darkening of the ground 
color into the adult shade, changes in shape and more complete fusions of some 
of the bands occur. As soon as the adult color has been attained, the dark mar- 
gins begin to develop. A specimen examined at this period shows that while 
no change has taken place in the form or extent of Bands I + II and III, Band 
IV has become outwardly angulated as in the adult, thus narrowing, especially 
in the middle of the wing, the white fascia separating it from V + VI. On the 
dorsal margin. Bands V, VI and VII are completely fused, the small white costal 
streak before the apex alone remaining to mark the position of the white fascia 
between V + VI and VII. The scales along the outer edges of Bands II and 
III are beginning to show faintly brownish tips, this color being about evenly 
distributed along the entire edge of Band II; in Band III, the color extends 
farther toward the bases of the scales in the middle of the wing. The scales of 
the dorsal half of the outer edge of Band IV are dark reddish brown, almost as 
in the adult, but on the costal half of the wing, there is only a very slight deepen- 
ing of the yellow color, the margin here being considerably paler than the margins 
of Bands II and III. There is a very slight deepening of scales on the outer 
border of Band V + VI, adjacent to the white streak before the apex. The 
dusting in the apex is dense, the color being darker and more blackish than the 
outer margin of Band IV, and extends from the white streak well around the 
apex and along the dorsal margin almost to vein 5. This dusting is considerably 
greater in extent even in this stage than that of the overwintering forms in any 
stage. 

Lithocolletis crataegella Clem. 

This species belongs to that large group in which the imago is characterized 
by the presence of pairs of opposite white costal and dorsal streaks; that is, all 
of the original primitive bands have fused at least along the middle of the wing. 
L. cratcegella (Fig. 36, PI. Ill) possesses in addition a margined basal streak, ex- 
ternal as well as internal margins to the white streaks (i. e., the dark scales 
developed on both sides of the primitive bands and not only on the outer side, as 
in the two preceding species), a streak of dark scales along the middle of the 
wing, a patch of black scales in the apex and the blue iridescence of the scales in 
the cilia. The study of the development of the wings in this form should there- 
fore throw light upon the origin and mode of development of the above characters 
and indicate their relative time of appearance. 

In the earliest stage examined (Fig. 12), at a period when the markings are 



128 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

pale yellowish and but little differentiated from the colorless wing, the pattern 
strikingly resembles that of the adult insect. The white basal streak is distinctly 
outlined, beginning at the base of the dorsum, where it seems to be homologous 
j^^jjfj. IV. V yj: with the white streak separating Bands I and II, be- 

yond this lying over a trachea which extends through 
' / the cell just above the middle; its tip seems to coincide 
with some portion of the white fascia separating Bands 
Fig. 12. Early stage in the II and III. The white patch near the base of the dorsum 
development of color in the wing • ^ identical with that in the adult and with the apex of the 

01 L. cratcegeUa. 

basal streak seems to constitute the last vestige of the 
white fascia separating Bands II and III. On the dorsal margin, the outer edge 
of Band III has shrunk away toward the base, and at the same time, there has 
been a compensating extension of Band IV toward the base, resulting in a dis- 
placement of the white streak, so that instead of being over vein 16, it is basal 
to it, and vein Ih reaches the margin well within Band IV. The first pair of 
streaks are already separated by a narrow line, which is not nearly as broad 
internally as in the imago. At this stage, the costal white streak is not much 
narrower on the margin than the dorsal. Bands V, VI and VII are situated 
normally, except that V on the dorsum extends a little basally over the tip of 
vein 2. These bands, while quite distinct on the margins and in the cilia, seem 
to fade away in the middle of the wing. The entire middle of the wing, from the 
tip of the first dorsal white streak almost to the extreme tip of the wing, remains 
colorless, so that it is not possible to distinguish the bands from the interspaces 
separating them. A comparison with the adult shows that this area coincides 
with that to be occupied by the dark streak of scales through the middle and 
by the apical patch of black scales. 

In a specimen somewhat more advanced, there has been a slight deepening 
of color, but by no means, even in the golden color, has the adult shade been 
attained. The color is still yellow, with no tinge of brown, unless the slight 
darkening of the dorsal side of Band IV, especially toward the second white 
streak, may be regarded as a foreshadowing of that color. The middle of the 
wing from the tip of the first dorsal streak almost to the apex (except for the 
grayish black scales to be noted below) still retains its whitish appearance. 
Just before the apex and beginning just under the tip of vein 7, and extending 
for a short distance along the underside of 7, are a number of grayish black 
scales. These appeared first beneath the tip of 7 and were gradually extended 
toward the base. The patch is broadest toward the apex, where it reaches al- 
most across the wing. The inner edges of the first pair of streaks are more curved 
than in the preceding specimen as a result of the broadening internally of the 
yellow line separating them. The scales attached around the apex are yellow 
and extend in an unbroken line to the second dorsal streak, that is, Bands V, 
VI and VII have united along the termen. However, the scales whose apices 
project beyond these and which are destined to constitute the iridescent blue 
line in the cilia still remain pure white. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 129 

A specimen at a somewhat later stage {Fig. 13) shows a httle more of the 
orange brown tint, but the color is nowhere as deep as in the adult. The formerly 
colorless area in the middle of the wing is still distinctly set apart from the rest 
of the wing but has become narrower and is beginning to acquire a faintly yel- 
lowish tinge. The white streaks are now definitely blocked out due to the 
curving in of the yellow color; they are, however, still connected with the whitish 
middle portion of the wing. The patch of blackish scales near the apex has 
increased in extent and depth of color until its identity with the patch of hlack 
scales in the apex of the adult wing is clearly established. It has now reached 
its adult condition, and no further change takes place. ^j^jf^ jv y ^,j 

The early origin and differentiation of this patch of ^^T-^-' 
scales shows clearly that it is a character quite sepa- ' ^ 

rate and distinct from the dark line of scales in the 

adult extending from it toward the base of the wing. Fig. 13. Later stage in the 
The scales around the apex, yellow in the earher stages, development ^f color in the wing 

*^ ^ of L. cratoegella. 

are now tipped with pale brown, but the outermost row 

of scales are still whitish as before. There is some deepening of the ground 
color just before the first and second pairs of streaks; the second dorsal streak, 
however, is the only streak which can be said to have acquired a definite mar- 
gin, and even this is pale brownish. The basal streak remains entirely un- 
margined. 

In a specimen at a little later stage than that just described, internal margins, 
though very pale, have appeared along all of the white streaks; that of the second 
dorsal still continues to be in advance of the others. The margin of the first 
costal streak has deepened somewhat, and there is a faint suggestion of gray 
around its tip. A similar pale gray shade extends from the tip of the first dorsal 
streak through the middle of the wing and around the tip of the second dorsal 
streak. The ground color along the upper edge of the basal streak is somewhat 
darkened, but there is no margin. 

In a wing at a considerably later period of development, the ground color 
approaches the adult color over those areas where there are no brown scales. 
The internal margins of the costal and dorsal streaks, as well as the upper margin 
of the basal streak, are dark brown; the external margins of these streaks and 
the margin around the tip of the basal streak while present are not as dark as 
in the adult and show a decidedly grayish tinge. This same gray color is pro- 
longed from the tip of the first dorsal streak along the middle of the wing in the 
area formerly colorless but is much paler than in the adult. This difference from 
the adult color is especially noticeable above the patch of black scales, where 
in the imago there is a decided deepening of color, almost blending with the 
black patch. There is but very httle deepening of color between the first and 
second dorsal streaks, and the margin of the second dorsal streak is neither as 
deep nor as wide as in the adult. The darkening of scales in the cilia started in 
earher stages stih continues. There is, however, no change from the colorless 
condition of the scales which are to be deep iridescent blue. 



^^ IT/ 



130 EVOLUTION OF COLOR PATTERN IN LITIIOCOLLETIS. 

The adult coloration appears to be attained several hours previous to 
emergence. At this time the markings are plainly visible through the pupal 
envelope. The bluish iridescence in the cilia is now well developed. Obviously 
this is one of the last characters to appear ontogenetically. 

Lithocolletis ostryaefoliella Clem. 

This species (Fig. 23, PL III) possesses an apical dot in its typical condition, 
composed of small black or blackish brown scales arranged in an almost circular 
shape over the tip of the wing. 

In the youngest specimen examined, the wings were dissected out at a period 
when they were losing their whitish appearance and becoming faintly banded. 
i,ii,m j^ V ,., The last four bands are straight and placed transversely 

on the wing, leaving colorless bands between them. The 

basal portion of the wing is exceedingly pale, and the 

ground color is scarcely discernible on the otherwise 

Fig. 14. Early stage in the colorlcss wiug. The Configuration of the color areas is 

development of color in the wing ^^^^ ^^^ ^^^^ ^^ -^ ^^^ ^^^^^ there being the Same 

of L. ostrycefokeUa. ' ^ 

outward angulation of Band III, internal to the first 
pair of white streaks. A stripe along the middle of the wing and a white spot 
on the dorsal margin remain colorless and mark the position of the basal streak 
and the white dorsal spot in the adult. 

At a slightly later stage, the markings just referred to have become a little 
more distinct; the color is still a very pale straw {Fig. IJj). The extreme base of 
the wing, while very pale, is still sufficiently contrasted with the unpigmented 
areas to show the outline of the basal streak defined for its whole length. On 
the dorsal edge, a pale shade broadest on the dorsal margin reaches two-thirds 
of the way across to the basal streak. On the basal side of this spot, the ground 
color seems a little deeper. Band III, although much angulated outwardly, is 
not yet connected in the middle of the wing with Band 

. . . i,7rjrr TV y VT ,,^^ 

IV; thus the first pair of white streaks are still con- ^^ 

nected and form an angulated fascia, broadest at its ^^ 

extremities. Bands IV, V, Viand VII remain entirely 

separate and retain their primitive straight edges, with Fig. is. Later stage in the 

the exception of the inner edge of Band IV which has "p^^^^* of color in the wing 

^ ^ 01 L. ostrycefoLieila. 

been somewhat produced toward the base at its ex- 
tremities. Band III and Band VII are possibly a shade darker than the other 
portions of the wing; the scales attached around the apex projecting into the 
cilia are, however, paler and concolorous with Bands IV, V and VL 

The ground color continues to darken, reaching its adult condition at a 
relatively earher stage than is the case in L. cratcegella. At the same time {Fig. 
15), the pale yellow spreads onto places originally unpigmented; thus the bands 
become connected by a paler yellow shade, so that the white fasciae are trans- 
formed into pairs of opposite narrow white streaks. At this stage in the develop- 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 131 

ment, there are four dorsal as well as four costal streaks. The apical dot is 
present, dark brown and almost as large as in the imago and very definitely 
outlined. Around the extreme apex, the scales projecting into the ciha are 
tipped with brown, this color being deepest just opposite the apical dot but 
quickly fading out on either side, so that it does not reach to the last pair of 
white streaks. The apical spot and these few scales around the apex are the 
only scales on the wing which show the slightest sign of brown; the bands are, 
however, a little deeper yehow on their outer than on their inner borders. 

Very soon after the stage just described, the dark margin of the second dorsal 
streak begins to develop; at this time, it consists of a few darker and shghtly gray- 
ish tinted scales somewhat removed from the dorsal margin. The apical spot 
is brownish black and seems to have reached its final development. The line 
in the cilia, though darkest immediately opposite the apical spot, is plainly visible 
from the fourth costal to the third dorsal streak, thus passing below the fourth 
dorsal streak which at this stage has almost disappeared owing to the fusion of 
Bands VI and VII. 

Very little change is now needed to reach the adult condition. The margins 
of the second pair of white streaks continue somewhat in advance of the others 
and reach their final stage of development a little earlier. All trace of a fourth 
dorsal streak finally disappears. 

LithocoUetis lucidico Stella Clem. 

At the time of the first appearance of a pale yellow tinge upon the wings, 
it is possible to discern faintly four bands in the apical half of the wing. Just 
before the apex within the area occupied by Band VII is a smah colorless spot. 
With the exception of the fact that these four bands are not connected along the 
middle of the wing, the adult color areas (Fig. 44, PL III) are now laid down. 
The dorsal portion of Band IV, the most proximal of these four bands, is con- 
tinued toward the base, as in the adult, by a pale yellow streak along the fold. 
Its costal portion is preceded by a white streak bordered internally by pale 
yellow which is extended along the upper median vein to the base. 

The apical dot is the first dark mark to make its appearance. While the 
yellow is still very pale, the scales of the formerly colorless spot near the apex 
begin to take on a grayish tinge. The deepening of scales over this area seems 
to take place in very much the same manner as that of the dark scales before the 
apex in L. cratcegeUa. 

The apical spot continues to deepen and increase in extent, reaching its 
adult condition before there is any indication of the formation of dark margins. 
The development of the apical spot is accompanied by a gradual and uniform 
deepening of the ground color together with the fusion of all the bands in the 
middle of the wing and of VI and VII on the termen. The middle portions of 
the wing between the apices of the white spots are somewhat paler, showing 
where the pigment has recently appeared. 



132 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

The darkening of scales in the ciha around the apex and just below it on 
the termen and the dark margins of the first costal and dorsal streaks are the 
next characters to appear. A wing examined at this stage shows the scales in 
the ciha brownish with scarcely a tinge of gra}^, the margin of the first dorsal 
streak somewhat paler and brownish yellow, extending from the ciha to vein 2, 
and the margin of the first costal streak pale and scarcely distinct. These 
observations are in agreement with those made on L. cratcegella and ostrycefoUella; 
namely, that the dark markings appear earliest in the apex of the wing on Band 
VII and soon after on Band IV. 

The process of development consists now merely of the gradual appearance 
and darkening of the margins of the other streaks and the extension of the line 
in the ciha to the first dorsal streak. 

LithocoUetis morrisella Fitch. 

At a period when the entire wing, viewed by transmitted hght, seems uni- 
formly colorless, the white markings as seen by reflected light are definitely laid 
down as they will appear in the adult (Fig. 48, PI. Ill) and have already acquired 
the lustrous pearly tint characteristic of the adult. This white appearance is 
due entirely to the structural modification of the scales described earher in this 
paper and cannot be in any way ascribed to a precocious development of the 
scales over these areas, since, when examined, all of the scales of the wing are 
seen to be fully developed. 

With the first appearance of pigmentation, a pale yellow suffuses those 

portions of the wing only which are destined to be yellow in the adult {Fig. 16). 

,,, ir V yt^yj, In the basal half of the wing, therefore, the yellow is 

confined mainly to the region above the fold; there is, 

however, a faint yellow tinge just before the dorsal arm 

of the fascia. There is a scarcely discernible tinge of 

Fig. 16. Early stage in gray at the basc of the dorsum below the basal streak 

the development of color in ^^^ ^^^^^^ ^^iQ first dorsal streak. At the tip of the wing, 

the wmg 01 L. morrisella. i o; 

over the area to be occupied by the apical dot, the scales 
are beginning to turn gray, those outermost being the deepest. Otherwise, the 
areas occupied by gray and black in the adult and by the white streaks appear 
by transmitted light uniform and colorless. Examination by reflected light 
shows that these two kinds of areas are not homologous, since the white streaks 
stand out clearly as structural modifications, while the scales margining them 
and those below the fold are duller and lack the pearly luster. The bands and 
the white fascia and streaks occupy their normal positions. The absence of a 
white streak over the apex of vein 7 is accounted for when it is seen that the 
apical spot has acquired such proportions as to cover the tip of vein 7, which in 
this and related species reaches the margin nearer to the apex than usual. 

In the next stage examined {Fig. 17), the ground color has deepened some- 
what, and decidedly more of the grayish tint has developed. The dorsal part 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 133 

of the wing below the fold, to be occupied by black scales in the adult, is pale 
gray; beyond the fascia where the scales are merely brown tipped, the color is 
still yellow, concolorous with the rest of the wing. Internal and external margins 
of the streaks are beginning to form simultaneously, ^^^ ^^ ^ 

those of the first costal streak are the deepest. The /^^. -'- ^ ; w^w 
change is direct from the colorless scales margining the .^ ^ 

white streaks to pale gray. The black streak in the fold 

beyond the fascia is at this stage composed of pale gray Fig. 17. Later stage in the 
scales. The apical dot is still pale gray, but the outer- development of color in the 

^ ± CT .7 7 wmg oi L. momsella. 

most row of scales is much darker and continuous on 

either side with a line of gray scales extending from the fourth costal streak 
to the third dorsal streak. The scales whose tips are to form the dark line in 
the cilia are still white. 

On the next wing examined, the gray has decidedly deepened along the dorsal 
margin, but the golden color has not reached its final condition. The develop- 
ment of the margins has progressed considerably, but now the internal are 
decidedly in advance of the external margins. The former have a blackish color, 
especially toward the costal margin; the latter are still grayish. The external 
margin of the first costal streak is deeper than that of the others. The black 
streak in the fold has practically reached its adult condition. The apical dot 
has increased in size and color until its extent is now definitely defined. The 
scales around its outer edge, which in the preceding stage were the only dark 
ones, are now black. The line in the cilia is gray, but there is no indication of 
the bluish iridescence. 

From this time on, no new characters appear, the development consisting 
only of a deepening of the colors to their adult condition. 

The sequence of colors and the relative time of appearance of the various 
adult characters is very much the same in L. robiniella as in the species just 
studied. The apical spot and the black streak in the fold reach their final 
condition at a somewhat earlier stage in comparison with the development of 
the other markings. 

Lithocolletis hageni F. and B. 

This species (Fig. 17, PL III) possesses a well-defined apical dot, very decided 
external margins to the white streaks as well as the usual internal ones and a 
dark margin along the upper side of the basal streak. The margin along the 
upper side of the white basah patch is regarded as homologous with the margin 
of a basal streak, that along its outer side with the external margin of the white 
streak primitively separating Bands II and III. The streak of ground color 
beyond the basal white patch is, therefore, the dorsal portion of Band III. 

Very few specimens of this species were available for study, but the obser- 
vations confirm in general those made upon the five preceding species. 

The apical dot appears well-defined and blackish at a period when Bands 



lU 



134 EVOLUTION OF COLOR PATTERN IN LITIIOCOLLETIS. 

V, VI and VII are still separated from one another by curved white fascise 
extending entirely across the wing and into the ciha {Fig. 18). The second 
pair of white streaks are still connected^ but Band IV is beginning to project 
i,jr,7n jjr ^- into them in the middle of the wing. At this time the 

'^" ground color of the wing is a pale straw and lacks alto- 
* ^ gether the golden brown of the adult. The internal 
margins of the first and second dorsal streaks are begin- 
FiG. 18. Wing of L. hagcni at ning to form. The inner edges of the bands^ border- 
the first appearance of the dark -^^ ^^^ ^^^^^^^ outwardly, present much the Same 

appearance as they do in species where the white 
streaks never acquire external margins; that is, the ground color fades gradu- 
ally into the white. 

A dark line in the cilia begins to form soon after this; the scales showing 
the brown pigment at this time are not those which will be bluish iridescent in 
the imago; these latter remain pure white and only acquire their pigment later. 

In the third specimen studied, the extent of the white streaks has been finally 
limited, and the golden brown color of the adult has been attained. AU of the 
internal margins of the streaks, the dark scales at the apex of the first dorsal 
streak, those connecting the tips of the second pair of streaks and the two leaden- 
colored lines of scales running across the wing from the tips of the third and 
fourth costal streaks are present. In addition, external margins are present 
on the white basal patch and on the first dorsal streak. All of these borders 
are as they will appear in the adult. In this specimen, there was no indication 
of a deepening along the upper side of the basal patch. However, this obser- 
vation cannot be accepted as altogether reliable in indicating the time of appear- 
ance of the margin of the basal streak, since the specimen was evidently ab- 
normal, the apical dot not being present. No other specimens were available 
to decide the point. Imagoes of this species are occasionally found which lack 
both the apical dot and the dark margin along the upper side of the basal patch. 

LithocoUetis aesculisella Cham. 

The species heretofore studied have been those belonging to the group 
having cylindrical larvae and characterized by the principal margins of the 
white streaks being internal. This species (Fig. 70, PI. IV) and those following 
have the so-called flat type of larva, and the white streaks of the imagoes have 
their darkest margins on the outer side. That is, in the former group, the 
tendency is for the color bands to acquire first, dark margins on their outer 
edges; in the latter group, the condition is reversed, and the dark color appears 
first on the inner edges of the bands. 

In L. cBsculisella, at a period when there is scarcely any differentiation 
between ground color and bands, the pattern appears to be laid down almost as 
in the adult (Fig. 19). The bands are very pale buff, and judging from their 
uniform color, appeared simultaneously. The pale shade at the base which 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 135 

separates Bands I and II extends entirely across the wing, but the early fusion 
of these bands on the costa is foreshadowed by the very faint tinge of buff just 
making its appearance in the costal portion of the pale fascia. On the extreme 
costa, Band V is indistinctly separated from VL Band VI is separated from 
VII by a white streak extending entirely across the wing. With these exceptions, 
the yellow marks are defined as in the adult. The white oblique dorsal streak 
extends just within the termen, being separated from the white streak before the 
apex as in the adult. The distal end of the oblique 

dorsal streak is probably homologous with the middle ^ ,-<- ' '^zjj:^..:-'^^'^ 
portion of the white fascia which in primitive types ; . "" 

separates Bands Vand VL In the imago, it sometimes 

exists as a separate small white spot before the apical Fig. 19. Early stage in the 
dusting and more proximal than the obhque costal development of color in the wing 

^ ^ PI 01 L. oBSCuhsella. 

streak. Along the termen, the cilia are of an unbroken 

yellow color, showing that at the extreme margin, there has been a complete 

fusion of Bands V, VI and VIL 

Before any of the dark margins begin to appear, the ground color deepens 
into the orange yellow of the adult. The external margin of the second fascia 
and the dark dusting at the extreme apex are considerably in advance of the 
other dark markings. The margin of the second fascia, formed by a dark line 
of scales along the inner border of Band IV, is most distinct in the middle 
portion of the wing and has not appeared on the extreme dorsal end nor on the 
costal end beyond the angle. Its color at this stage is brownish. In one speci- 
men, the apical scales are not as dark as the margin of the second fascia; in another 
of the same age, as indicated by the state of development of the margins, the 
dusting of the apex is somewhat darker than the margin of this fascia; in both, 
however, the brownish tint is confined to the extreme apex. There is a slight 
darkening of the scales in the middle of the wing on the inner border of Band III 
adjacent to the first white fascia and along the under side of the oblique dorsal 
streak. 

The dark margins of the fascise and of the obhque dorsal streak continue 
to develop, but before they reach their adult condition, the scales on the outer 
side of the costal spot over vein 10 begin to darken. At this time, the apical 
dusting is still confined to the apex of the wing and is not extended along the 
termen toward the tornus. This extension of the dusting toward the tornus is a 
characteristic of specimens appearing in the summer and does not occur in forms 
from overwintering chrysahds. It develops after the other adult characters 
have appeared. 

Lithocolletis bethunella Cham. 

In the youngest specimen examined, the ground color is a uniformly pale 
ocherous, and upon it the extent of the adult markings (Fig. 84, PI. IV) is quite 
definitely blocked out (Fig. 20). The white fascia (or second pair of streaks) 



136 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

is, however, prolonged outwardly at its angle along the wing to a position between 
the third pair of streaks. A comparison with the adult shows that the pro- 
longation of the fascia is occupied by dusting on a whitish ground; that is, these 
j.^^^ ni jy- y^y^ white scales are destined to become black tipped. 

The third pair of streaks are situated normally over 

I veins 10 and 2 respectively. There is no white spot 

^ over the tip of vein 9 on the costa. Bands V and VI 

Fig. 20. Early stage in the havc fuscd. A quadrate area in the apex remains 

orZtZ*;°'"^ '-^ *'^ ^'"^ ««loriess; the portion directly over vein 7 corre- 

sponds to the white streak normally situated here, 
the remainder will be occupied by dark dusting in the adult. The scales 
around the margin at the apex are yellow; these in the adult will be brown 
tipped yellow scales. 

In a wing at a somewhat later stage, there has been some deepening of the 
ground color. There is a small patch of scales just beyond vein 7 which are 
brown tipped and darker than any other scales on the wing. In the extreme 
apex, the scales extending over the cilia are not noticeably dark tipped. Dorsal 
to the dark patch of scales, the scales over the formerly colorless area become 
gradually paler, until near vein 5 their tips show just a faint tinge of gray. All 
the scales in the prolonged portion of the fascia are becoming pale gray tipped. 
There is also a faint gray tinge to the scales just below the tip of the dorsal 
arm of the fascia, continuous with the gray in the prolonged portion of the fascia. 
All of these scales are much paler than those in the apex just beyond vein 7 but 
approach in color those near vein 5. 

The margins of the remaining streaks soon make their appearance; the 
dusting of the apex reaches the adult condition earliest. 

A contrast in the sequence of development of dark marks is afforded by 
L. carycefoliella Clem. In this species, the margins of the first and second fasciae 
develop contemporaneously with a small patch of dusting at the extreme apex, 
and the margin of the second fascia is entirely complete, though not as dark as 
in the adult, at a stage when there is no indication of dark dusting beyond its 
angle. This dusting is very variable even in the adult, sometimes being very 
slight. The significance of the difference in development will be discussed later. 

LithocoUetis ulmella Cham. 

In this species, the pale yellow color appears simultaneously over all those 
areas which are to remain yellow in the adult (Fig. 95, PI. IV) or in which the 
scales are yellow with brown or blackish tips. The white streaks and the white 
dusted portions of the wing remain colorless. Thus, the second costal streak is 
produced for a short distance along the cell, and the wing from vein 7 to the 
apex is colorless, but the scales around the apex and below the oblique dorsal 
streak, which are yellow with brown tips in the adult, have already acquired the 
pale yellow color. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 137 

In the next stage studied^ the color has become almost as deep as in the 
adult. A number of the scales projecting from the extreme tip of the wing over 
the cilia are brown tipped; these are continued in a broken line through the cilia 
to the tornus. Over the wing membrane near the apex, in the area which was 
transparent in the earlier specimen, the scales are becoming dark tipped. These 
scales are deepest toward the apex of the wing, becoming very pale gray toward 
the tornus external to the oblique dorsal streak. A few scales along the costa 
corresponding in position with the dark scales in the adult are beginning to show 
darker tips. The scales margining the first and second costal streaks, which were 
whitish before, are now faintly gray. The color is uniformly developed over the 
whole margin and on the prolonged portion of the second streak. 

In a specimen a little further advanced than the one just described, the apical 
dusting is almost as in the adult. This darker color does not quite reach the 
tornus; that is, the external edge of the white dorsal streak is stih margined by 
pale gray scales as before. The margins of the first and second costal streaks 
have scarcely changed in color, but the scales in the prolonged portion of the 
second streak have darkened more rapidly; they are decidedly gray but much 
paler than those in the apex. The only new character which has appeared is 
the dark line through the cilia. 

Lithocolletis hamadryadella Clem. 

In the earliest stage examined {Fig. 21)^ the basal third of the wing is almost 
colorless. At the extreme base on the costal margin is a small patch of pale 
yellow scales, and a little beyond it another similar patch. These two patches 
of scales form Band I. Beyond these is a somewhat larger patch of pale yellow 
scales. This is the inner portion of Band II; the line of scales which marks its 
original outer limit in the adult (Fig. 77, PL IV) has not yet acquired any pig- 
ment. Band III at this stage is represented by a rather narrow angulated band 
which extends across the wing some distance before the tip of vein 16. The 
white projects into its angle on the inner side. Band IV is composed of two 
separate patches of yellow scales, one on the costa and the other on the dorsum. 
Their pointed apices lie over the bases of veins 10 and ^^^ 

2 respectively, the normal position for Band IV, but - "^^ ^ ^^^ 

on the margins, they curve back toward the base so > 

that they are much farther removed from the tips of 
the veins than usual. The middle of the wing to the ^^ 

apex is colorless. Band V + VI is represented by a ^^^- ^i- Early stage in the 

, 1 r* 1 'ii • rrn 1 1x1 development of color in the wing 

patch of scales on either margm. The dorsal patch of l. taadr^a^a. 
originates just beyond vein 2 and extends over vein 

5; the costal patch originates on the cell about midway between veins 10 and 
9 but extends obliquely outward so that the inner edge on the costa is just basal 
to vein 9 and the outer edge just before vein 7. The white streak over the tip of 
vein 7 is very narrow, and its corresponding dorsal streak is indistinct. The 



138 EVOLUTION OF COLOR PATTERN IN LITLIOCOLLETIS. 

cilia belonging to Band VII are all yellow with a few white scales here and 
there extending into them. Bands VII, V + VI and IV are somewhat deeper 
than Band III; Bands I and II are very pale, their paleness being caused by 
the large admixture of colorless scales at this stage. 

In the next specimen examined, apart from a slight deepening of Band III 
and those beyond it, the only changes observed are the following. The two basal 
patches on the costa, belonging to Band I, show a slight admixture of brownish 
tipped white scales. The third patch (Band II) is now faintly continued to 

the dorsum by a line of scattered yellow scales, and just 

1 ^^ ^'^^^ m beyond it, in the position normally occupied by the 

'7 '^'"'^ outer margin of Band II, is an angulated line of very 

faintly yellow scales. This marks the original outer 

, -' limit (phylogenetically) of Band 11. Just before the 

Fig. 22. Later stage in the tip of vciu 16 is a similar line of scalcs running parallel 

development of color in the wine , ,i i i r* t~» i ttt i i • -j i 

of L. hainadryadeiia. ^^ ^^^ dorsal arm 01 Band III and markmg its outer 

limit. These two lines of scales sometimes do not ap- 
pear until a much later period in the development. Their time of appearance 
is largely determined by the number of yellow scales mingled with the dark 
scales in the adult, since it is only in the yellow scales that the pigment ap- 
pears early. 

In the next stage studied (Fig. 22)^ Bands I and II in the basal part of the 
wing remain practically unchanged. Band III is the same in extent, but its 
color has deepened. Its internal margin is beginning to form, the scales adjacent 
to the yellow becoming gray tipped. The gray pigment appears directly in 
the whitish uncolored scales of the previous stage without passing through any 
of the intermediate steps. In general, the margin is broadest on the costa, be- 
coming narrower and paler below it, and not easily distinguishable toward the 
dorsum. On its inner edge, the margin is straight or slightl}^ curved as in the 
imago; on its outer side, the scales project into the angle of the band and fill 
up the formerly colorless space. The tips of these scales are darker than those 
of the margin elsewhere. In this specimen, there are only a few scattered yellow 
scales beyond Band III and no indication whatever of the dark line of scales 
which is to appear later. The internal margin of Band IV is well marked on its 
dorsal half, consisting of several rows of dark tipped scales as in the imago. It 
curves between the two yellow patches, extending to their apices, but not beyond 
them into the colorless fascia. The costal half of the margin consists only of a 
few pale gray scales and does not quite reach the dorsal half of the margin. 
Except for a few very faintly grayish scales above the termen on the inner edge 
of the dorsal part of Band V + VI, there is no indication whatever of any dark- 
ening of scales adjacent to Band V + VI. Belonging to Band VII, and begin- 
ning just behind vein 7, the scales covering the entire apex of the wing are gray 
tipped. Some of them, especially on the costal margin, project over the yellow 
scales which are to form the line in the middle of the cilia. The gray tipped 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 139 

scales of the apex, those between the two parts of Band IV and in the angle of 
Band III. are darker than the other scales forming the margins. 

In a specimen at a considerably more advanced stage of development, the 
scales composing the two patches at the base of the costa are entirely gray tipped 
and very much the same as they will appear in the adult. The colorless scales 
mingled with those forming the proximal part of Band II are beginning to be 
gray tipped; this is especially noticeable on the quadrate part above the upper 
median vein; below it, there is only a line of a few scattered gray tipped scales 
reaching to the dorsum. The line of scales beyond, forming the original outer 
limit to Band II, is pale gray tipped throughout and, though broader on the costa, 
is complete to the dorsum. The broadening of the internal margin of Band III 
has continued. Its external margin, separated from the yellow band by white, 
is indicated by a single line of pale gray tipped scales running from the costa to 
the cell. The internal margin of Band IV has broadened and deepened and has 
now probably reached its adult condition. It is not possible to determine 
whether the development is completed in any single specimen, since there is a 
great deal of variation in the amount of dusting among the different individuals 
in this species. In this stage, the scales which in the imago are the most distal 
of those forming the dark external margin of Band IV are tipped with pale gray 
and connect with the dusting between the costal and dorsal parts of Band IV. 
Those on the inner side of the margin which will in a great measure fill up the 
white space between the margin and the yellow parts of the band are still un- 
colored. There is a very considerable patch of dusting internal to Band V + VI 
on the dorsal margin and connected with the apical dusting which has been 



IV 



V+VI 



extended proximally between the parts of V + VI. ri l^~ „ ,.,, 

The costal dusting is not nearly as dark and is some- ^-"^^^^"^ ^f^^^. 

what scattered. In addition to the extension of the 

apical dusting proximally, there has been an increase 

in the number of dark scales mingled with the cilia. Fig. 23. Wing of l. immadry- 

The dark line through the middle of the cilia formed ^^'"^ ^^^^ ^^^ ^^^ ^^ ^^^ p^p^^ 

state 

by brown tipped yellow scales is now quite distinct. 

At this time, most of the dark markings are at least definitely defined in posi- 
tion; there is needed to bring them to their final state only a darkening of those 
scales already gray tipped and in some places the appearance of pigment in 
other scales adjacent to these. 

In a specimen to be described now, most of these characters have appeared 
{Fig. 23). The patches of dark gray scales at the base of the costa and the hne 
of scales beyond the third of these patches have increased and darkened decidedly. 
The line of scales external to Band III has now become dark gray tipped. Ex- 
ternal to Band IV, the dusting has been extended toward the base, so that only 
a small white streak is left between it and the band on the margins. The dusting 
in the apex has been much increased and extends along the margin, especially on 
the costa, and connects with the internal dusting of Band V, thus almost obhter- 
ating the white streak over vein 7. 



140 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

Cremastobombycia ignota F. and B. 

In the youngest specimen examined^ one in which the ground color was pale 

yellow^ the extent and position of all the adult markings (Fig. 62, PL IV) is defined 

{Fig. 2Jj) . The paleness is especially marked toward the apex, where it is difficult 

r,r to distinguish the markings at all. The white fascia 

III l^ V+J/I [77 . 

^^^^ is considerably broader than it will appear later. A 

careful examination shows it to be composed of two 
parts, an inner fascia which is to form the white fas- 
cia of the adult and in which the scales are whiter 

Fig. 24. Early stage in the de- ^j^^ ^^^ f^^y formed, and an outcr fascia, where the 

velopment of color in the wing of , ,1 n i i i i 

(7 ignota. scales are not as large nor as well developed and are 

somewhat buffish in color. These scales will later 
form the black scales of the margin. This same thing is true of the other 
streaks but is not as noticeable except in the case of the first costal because of 
their more irregular shape. The band between the pair of streaks at three- 
fourths of the wing length and the streak enclosing the apex is, as shown by its 
position, equivalent to Band V + VI. The white streak before the apex is situ- 
ated over the tip of vein 7. 

In a later specimen, the ground color has deepened to that of the adult. 
The scales in the apex and in the cilia remain concolorous with the wing and are 
not darker at their tips. The dark external margins of the white fascia and 
streaks are appearing simultaneously, and all are equally advanced. The 
scales forming them correspond in position with the colorless scales which formed 
the outer part of the fascia in the preceding stage. The pigment, which is pale 
gray without a tinge of yellow or brown, is evenly distributed throughout the 
entire scale from the base to the tip. None of the internal margins has appeared. 

In a later stage, the external margins are black as in the adult, and internal 
margins are present on the costal end of the first white streak and the fascia. 
There are no internal margins on the pair of streaks at three-fourths. As 
margins of these streaks are not always present in the imago, it is impossible to 
determine conclusively whether they normally appear after the internal margins 
of the fascia and the first streak. However, as will be shown later in the dis- 
cussion, variable characters tend to appear later in the ontogeny than the fixed 
characters of a species. 

The observations on the development of color in the wings of C. solidaginis 
(Fig. 60, PI. IV) agree very closely with those on the preceding species. The 
configuration of the color areas at their first appearance is the same as that of 
the adult. In this species, however, the scales which are to form the dark 
margins in the adult are pale yellow instead of, as in ignota, being colorless 
and not fully formed. A comparison with the adult shows that these are 
dark tipped yellow scales, the dark pigment being found at the tip of the scales 
and not, as in ignota, almost uniformly distributed throughout the entire 
scale. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 141 

4. Discussion and Conclusions. 

In general, I have found that the action of three processes is sufficient to 
explain the transformation of the seven primitive bands into the several existing 
patterns of the ground color. These three processes may be stated thus: (a) The 
middle portion of a band may be produced distally until it comes in contact with 
the band beyond it. (6) The extremities of a band may be broadened by being 
produced proximally. (c) The extremities of a band may be narrowed by the 
retraction of pigment from their outer edges. These three processes may act 
separately or in combination; the particular pattern produced is the resultant 
of their combined activity. The first two of these laws are based chiefly upon 
the changes observed during pupal development, the third law is deduced 
from adult characters, since the changes are such as cannot be observed directly. 
The evidence in detail is as follows : 

In L. tiliacella {Fig. 7), seven distinct transverse bands of ground color 
are laid down; of these, those numbered II, III and IV appear first; following 
these, Band I, at the base of the wing, appears continuous in the costal half of 
the wing with II; it is, however, sufficiently separated from it by the difference 
in time of appearance. The three bands in the apex of the wing appear last and 
undergo no change; the connection of Band V with IV is brought about entirely 
by the extension outwardly of IV along the middle of the wing. The changes 
in Bands II and III are brought about by the spreading of the color onto areas 
formerly unpigmented; that is, the fascia between II and III is narrowed by 
the very slight growth distally of II along the middle of the wing, its extremities 
remaining fixed, and by the extension proximally of III, chiefly along the margins. 
Band IV reaches its adult configuration earhest; it is also the earhest to acquire 
the black pigment on its outer edge. This does not appear in the middle of the 
wing, where the band has extended outwardly uniting with V. The outer 
edges of the extremities of Band III have remained constant in position, and the 
dark scales appear first here. In Band II, there has been the least change in 
shape; the deepening of the pigment along its outer edge occurs more uniformly. 
From this, it follows that while the general tendency is for dark pigment to develop 
along the outer edges of hands adjacent to unpigmented areas, the precise time of its 
appearance along any hand or portion of a hand in relation to other hands or portions 
of the same hand is determined hy the time when such hands or portions of hands 
reach their adult shape and color. The outer edge of a hand in direct contact with 
another hand acquires no dark pigment. It would appear from the observations 
on this species that the hands in their primitive condition are narrower than they 
are in the adult. A fascia may he narrowed hy the uniform spreading of a hand 
toward the hase. 

These conclusions are corroborated by the observations on L. tritcenianella 
(Fig. 5, PI. Ill) ; all the bands, however, appear simultaneously, and at this time 
all are straight. There is, however, a reduction in the apparent number of bands, 
V and VI being completely united. Band IV seems no further advanced than 



142 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

the others toward the adult condition; as in tiliacella, development must take 
place more rapidly, since its margins reach their adult condition before those 
of the other bands. Here, also, is the first manifestation of that tendency, so 
characteristic of all the more highly differentiated species of the genus, toward 
the darkening of scales in the apex. In this species, these scales are scattered 
over the entire apex, instead of being limited to a definitely defined area where 
the scales are modified structurally. This species does not, at any stage, show 
the primitive type of marking; a considerable amount of development is, however, 
necessary before the color areas attain their definitive final extent. 

In L. cratcegella (Fig. 36, PI. Ill), ostrycefoliella (Fig. 23, PL III), lucidicostella 
(Fig. 44, PI. Ill), hageni (Fig. 17, PL III) and morrisella (Fig. 48, PL III), in the 
basal half of the wing, where in the adult there is the greatest divergence from a 
transversely banded type of marking, the color areas, upon the first appearance 
of a uniform pale yellowish, have almost exactly the same shape and extent as 
in the adult. They undergo very little change during development, except that 
in these species, as weh as in tiliacella and tritcenianella, there is a progressive 
and gradual deepening of the ground color. In the youngest specimens of 
ostrycefoliella observed (Fig. I4), the first pair of streaks are still connected; 
very soon, however, they become separated by the union of Band III with IV. 

In the apical half of the wing. Bands V, VI and VII appear as straight 
transverse bands (except in morrisella) ; the transformation of the unpigmented 
fasciae between them and between IV and V into pairs of opposite streaks is 
brought about by the outward extension of Bands IV, V and VI along the cell 
in a manner similar to that previously observed for Band IV in tiliacella and 
tritcenianella. The obliteration of a white streak is brought about by the inward 
extension of the extremity of a band to meet the outer edge of the preceding 
band. In morrisella, the pattern is predetermined from the outset, the white 
fascia and streaks being produced by structurally modified scales, which are 
destined never to acquire pigment. 

There are no reasons favoring the view that such a type of marking as that 
found in cratcegella (Fig. 36, PL III) is primitive: there are many reasons for re- 
garding it as having been produced through a long process of evolution. It is a 
matter of general observation that the pale colors appear first ontogenetically, 
black of the pigmental colors being last to appear; it has been inferred that the 
same is true also for the phylogeny. In the adults of these species, there have 
developed, in addition to the usual dark markings adjacent to the unpigmented 
areas, definitely limited black spots and streaks in the apex. The scales thus 
pigmented are also differentiated structuraUy from the surrounding scales by 
their smaller size. There is no such structural modification of the dark tipped 
scales in the apex of tritcenianella. Obviously a considerable period of time 
must have been required for the final differentiation of such characters as these. 
That these species have undergone an extensive process of differentiation in the 
production of certain characters of a kind which can only be acquired late in 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 143 

racial development, renders it highly probable that there has also been a far- 
reaching modification from the ancestral condition of the extent of the color 
areas. These phylogenetic changes are scarcely or not at ah repeated in the 
ontogeny. Three primitive bands are still preserved during the early stages 
in the apex of the wing; the band proximal to these shows unmistakable signs 
of its origin from a straight transverse band, its outer edge being straight. We 
may, therefore, with reasonable certainty, conclude that the color pattern of 
the basal part of the wing may be traced back through a series of phyletic changes 
to its origin from the first three primitive bands. 

The ontogeny offers no direct testimony of the means by which these results 
have been accomplished; it has given, however, visible evidence of two actual 
dynamic methods by which changes have been wrought; namely, the middle 
portion of each hand may he produced distally until it comes in contact with the 
hand heyond it; the extremities of a hand may he hroadened hy heing produced proxi- 
mally. Thus are produced, first, angulated fascise; second, slightly obhque 
pairs of opposite streaks; the final effect of the second of the above processes, if 
acting alone, is the entire obhteration of the white streaks. That a third process 
has been at work is indicated by observations upon adult forms. The dorsal of 
the first pair of white streaks in L. cratcegella (Fig. 36, PI. Ill) does not occupy its 
primitive position over vein 16 but has been displaced toward the base, and vein 
16 reaches the margin within Band IV; that is, there has been an extension of 
the extremity of Band IV in this direction over the area formerly white. But 
since a white streak still remains, there must have been a compensating drawing 
away of the outer edge of Band III at its extremity. Such a withdrawal of 
pigment cannot, of course, be observed ontogeneticahy. A third dynamic process 
in the transformation may, therefore, be stated thus : the extremities of a hand may 
he narrowed hy the retraction of pigment from their outer edges. This is an example 
of the shrinking away of a band at one end. In this case, the shrinking takes 
place at the outer edge of the band only. The result of the combined action of 
the second and third of these processes is the progressive movement of the 
end of the band toward the base. 

These three processes are sufficient to explain the origin of all the types of 
marking in this genus; the specific results in any case are due to the manner and 
extent of their action; that is, whether they act singly or together and to the relative 
rapidity of action of the three processes. How they have combined to produce 
these various types will be discussed in detail under the heading of phylogenetic 
development. 

In the second division of the genus, the extent of the areas of ground color 
undergoes very little change during development. The ground color appears 
in the earhest stages over those areas which in the adult are occupied by yellow 
or reddish yellow scales or by dark tipped yellow scales. The scales, which in 
the adult are white with dark brown, gray or black tips, do not receive pigment 
until much later; they then pass directly to gray or brownish gray and thence to 



144 EVOLUTION OF COLOR PATTERN TN LITHOCOLLETIS. 

black, without passing through the intermediate yellowish and brownish shades. 
The tendency for dark pigment to develop along the edges of bands adjacent to 
unpigmented areas is exemplified in this group also, with this difference, however, 
that it appears first along the inner edge of a band. When dark pigment develops 
in addition along the outer edge, it appears at a later period. The converse is 
true in the first division of the genus; the dark margin appears earlier on the 
outer side of a band. I can offer no explanation of the original cause of the 
difference in direction of development; the result in either case seems to be the 
expression of the same general tendency in development, acting, however, with 
different degrees of intensity on either side of a band. It would seem that the 
development of unusually dark pigment on one side of a band — the acceleration 
of chemical processes over a localized area — retards development on the other 
side. 

The ontogeny within this division affords very little evidence of the operation 
of the first two processes of evolution defined earlier in this discussion. However, 
the shape of the bands and the separation of the white fasciae into opposite spots, 
with the total obliteration of some of the spots, is sufficient proof that these forces 
have acted during the evolution of the species. 

L. hamadryadella (Fig. 77, PL IV) alone, of those observed, shows the out- 
ward prolongation of the middle of a band; the gradual extension distally of 
the dark dusting between the dorsal and costal portions of Band V + VI and 
its final contact with the apical dusting (Figs. 22, 23) is an example of the 
working of this law. The third law postulated to explain the displacement of 
oblique streaks toward the base receives decisive confirmation from the adult 
markings of the same species. A narrow line of scales crosses the wing beyond 
the yellow portions of each of Bands II, III and IV, being separated from them 
by white. These scales occupy positions corresponding to the outer margins of 
these bands; ontogenetically, the dark pigment develops in them after it has 
appeared on the inner margins of these bands. The conclusion is apparent that 
these lines of scales mark the earlier phylogenetic limits of these bands. The 
bands have shrunk away, most rapidly on the costa and dorsum, leaving behind 
them the margins as visible evidences of the process. 

In L. tiliacella {Fig. 7), which, from its conservation of the greatest 
number of bands in a primitive straight condition, the very pale ground color 
and the entire absence of any dark scales in some of the bands, may be regarded 
as the most primitive of the American species, there is a difference in the time 
of appearance of the bands. In the more advanced species, the bands appear 
at the same time. Evidently, then, in the higher species, there is a hastening 
and crowding together of the earher stages, so that the bands which formerly 
appeared in sequence now appear contemporaneously. Those in the apex of 
the wing, which have experienced the least modification during the phylogenetic 
development of the species, alone recapitulate the racial history during their 
ontogenetic development. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 145 

The discussion heretofore has dealt chiefly with the processes which effect 
the final limitation and configuration of the ground color. The general tendency 
toward the production of dark pigment in rows of scales adjacent to unpigmented 
areas has also been noted. These streaks of dark scales, which are usually 
transverse, and the various other characteristics, such as the apical spot, the 
longitudinal streak of black scales in the apex and the black streak in the fold, 
properly constitute the markings^ in distinction to the ground color, and are 
superimposed upon it. While the progressive change in the configuration of 
the ground color is the important factor in determining the general evolution of 
the genus and the different stages at which development has halted form the 
starting points for the differentiation of the different groups of species, the develop- 
ment of the markings is the important factor in determining the phylogenetic 
sequence of the individual species within each group. A knowledge of their 
mode of origin and relative time of appearance is therefore essential. 

In L. tiliacella and tritcenianella, it was seen that the dark margin develops 
first along the edge of Band IV, which is the first band to reach its adult shape. 
In L. tiliacella, the outer edge of this band has become fixed before all of the bands 
have even been laid down. The dark margin appears toward the costa and 
dorsum, in places where the outer edges of the band have undergone no change 
whatever since the first appearance of color. The dorsal margin seems to be 
in advance of the costal. There is no darkening of pigment along the bands in 
the apex, which appear comparatively late. From these observations, it appears 
that in the ontogeny, the dark margin develops earliest along the edge of that band 
which first reaches its definitive adult condition. Before dark margins can develop, 
the edge of a band must have remained fixed for an appreciable period of time. 

In L. cratcegella, ostrycefoliella and lucidicostella, the dark margin on Band 
IV is also the first to appear. The apparent contradiction to the principle just 
laid down that a dark margin develops earhest along the edge of the band that 
has first reached its definitive adult condition, lies in the fact that in these species 
the color areas in the basal half of the wing are at the outset defined almost as 
in the adult, while the bands in the apex repeat the racial development. It 
might be expected, then, that the margin would appear earhest along the first 
pair of streaks. It has, however, required a much longer time in the evolution 
of the species for the basal half of the wing than for the apical half of the wing 
to acquire its present aspect; the development in the apical half has come to a 
standstill comparatively early in the phylogenetic history of the species. The 
observed recapitulation in the apical three or four bands during the ontogenetic 
development of the steps in the racial differentiation of the species is in harmony 
with the conclusions of other investigators that it is only among primitive forms 
that anything approaching a complete repetition of phylogenetic changes is to 
be found in the ontogeny. 

The apex of the wing (in respect to the conservation of primitive color 
areas) may be regarded as primitive in comparison to the base of the wing. In 



146 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

the phylogenetic development of this type of marking^ therefore, it is possible 
that the margins appeared on Band IV while the basal half of the wing was still 
under the influence of dynamic forces producing constant changes in the out- 
Unes of the areas of ground color. No margins could have appeared in the basal 
half of the wing until after these outlines had become permanent. Some of 
these changes, as has been already shown, are such as cannot be repeated during 
pupal development. Hence the color areas in the basal half of the wing tend 
to be laid down in their final shape. The sequence of the appearance of dark mark- 
ings, which are in reality a second series of transverse hands superimposed upon an 
earlier set, follows the same order for the ontogeny as for the phytogeny; that is, in 
this second and more recent set of characters, there is an actual recapitulation. The 
margins of Bands V and VI appear later, corresponding, therefore, to the sequence 
in the time of appearance of these bands phylogenetically, hypothetically based 
upon that of L. tiliacella. The margin on the upper side of the basal streak 
corresponds in time to the outer margins of the bands; it appears before inner 
margins develop. An outer margin of a band tends to appear first near the costa 
or dorsum, an inner margin near the middle of the wing; that is, at the apex of 
the outer side of a white streak, these being the parts of the edges of the bands 
which have reached their permanent position earliest. Therefore, the relative 
time of appearance of the dark margin of any band in the ontogeny is dependent 
upon the time when the edge of that hand hecame fixed in the phytogeny. 

InL. morrisella (Fig. 48, PL III), margins are formed almost simultaneously 
on either side of the white streaks by a direct change to gray and thence to black. 
The pigment in the other black scales develops in a similar manner without 
passing through the usual intermediate stages. The gray and black pigments 
make their first appearance at an early stage, while the ground color is still 
pale yellow. The structural differentiation of the white scales, the massing of 
black scales in the dorsal half of the wing, the exceedingly large apical spot and 
the black longitudinal streak in the fold all indicate the very high phylogenetic 
position of this species. Upon the addition of these newer characters, the earlier 
ones were crowded closer together and pushed farther back into the ontogeny, 
resulting in their contemporaneous development. 

In the species of the second division of the genus, dark margins develop in 
conformity with the principles already enunciated. There are certain minor 
differences between this and the preceding division attendant upon the original 
unexplained diversity in the inherent tendencies of the two divisions. The dark 
margin appears first on Band IV in the middle of its inner edge, in contrast to its 
appearance in the other division on the outer side and near each end of this band; 
the same is true for Band III. This is a necessary consequence of the action 
of the three general processes of evolution; the middle of the inner edge of any 
hand remains stationary, and hence a margin will develop here earlier than at the 
extremities of the hand. 

In Cremastohomhycia ignota (Fig. 62, PI. IV), the development is very similar 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 147 

to that of the species of the '^flat-larval group.'' The margins appear almost 
simultaneously^ the scales changing directly from colorless to gray and thence to 
black. These scales, at the time the yellow ground color spreads over the wing, 
are not fully formed, thus contrasting with the similarly unpigmented, but 
fully developed scales belonging to the white fascia and streaks. In all other 
species examined, the scales were all equally and fully formed at the time of the 
first appearance of pigment in any part of the wing. 

In many species, these dark streaks adjacent to white are the only defined 
dark markings present; there may be a few scattered, darker tipped scales in 
the apex. An increase in the amount of dark pigment producing additional 
dark markings manifests itself in either of two ways. (1) The number of scales 
thus affected may be increased, so that the actual extent of the wing occupied 
by dark tipped scales is greater. This is the direction that evolution has taken 
in the species of the '' flat-larval group'' (illustrated on Plate IV) and in a few of 
the species of the '^ cylindrical-larval group" {e. g., celtisella, Fig. 56, PL III, and 
celtifoliella, Fig. 4, PL III). Often, among the more highly differentiated of the 
species of the '^ flat-larval group," the entire apex of the wing is covered with 
black tipped scales {e. g., agrifoliella^ Fig. 79, PL IV). Similar areas may develop 
in other parts of the wing; thus a patch of dark tipped scales may extend outwards 
from the angle of a fascia (e. g., bethunella, Fig. 84, PL IV). (2) There maybe a 
concentration of pigment in comparatively few scales, which with increasing 
differentiation tend to be segregated in definitely limited areas marked out by 
structural modifications of the scales (e. g., lucidicostella, Fig. 44, PL III, and 
cratcegella, Fig. 36, PL III). In these cases, the scales are pigmented almost to 
their bases, not merely dark tipped. With the single exception of obstrictella 
(Fig. 64, PL IV) among the species of the second division of the genus, this 
tendency is confined to the species of the '^ cylindrical-larval group," where it 
manifests itself in the apex either as an apical dot or as a somewhat elongate or 
irregular patch of scales, broadest just before the tip of the wing. A similar 
longitudinal streak of black scales is present in the fold in robiniella (Fig. 50, 
PL III), uhlerella (Fig. 49, PL III), and morrisella (Fig. 48, PL III). 

Finally, there may be a decided deepening of the ground color itself between 
the white streaks. This process has reached its highest development in robini- 
ella, uhlerella, and morrisella. 

In the ontogeny, the development of all of these specializations has been 
much abridged, and concomitant with this, their time of appearance has been 
pushed back farther and farther into the earlier stages of pupal development. 
The dark tipped scales remain colorless during the time the yeflow scales are 
attaining their adult condition; later, they change directly to gray and black. 
The pigment in the areas of dark tipped scales in the apex and beyond the fascise 
often appears simultaneously with that of the margins. Some variation is to 
be noticed here; in L. bethunella, the gray pigment appears in all the scales 
beyond the fascia, simultaneously with the beginning of the formation of the dark 



148 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

margin; in L. carywfoliella, the dark margin of the fascia is complete before any 
pigment has developed in the area beyond it. In the imago, the patch of dusting 
beyond the fascia is an estabhshed constant character in hethunella; in carycejo- 
liella, the amount of such dusting is very variable, indicating its recent appearance 
in the species. 

It would seem then that only those characters permanently established and of 
long standing in a species exhibit this precocity of development; recently acquired or 
variable characters appear ontogenetically in the order of their phylogenetic sequence. 

This conclusion is confirmed by observations upon the mode of development 
ontogenetically of other analogous dark markings. Comparison of imagoes 
indicates that the apical spot and the black patch in the apex have originated 
phylogenetically earher than the streak of brown scales along the middle of 
the wing but later than the dark internal margins of the white fascise and streaks. 
In L. crata^gella, the pigment in the scales of the black patch before the apex, 
which is unquestionably a characteristic only acquired through differentiation 
extending over a long period of time, appears earlier than that in the brown 
scales extending along the middle of the wing and reaches its definitive adult 
condition while the latter are still wholly unpigmented. In L. hageni also, the 
apical spot appears sooner than the dark scales in the middle of the wing beyond 
the tip of the first dorsal streak. 

Such specializations as these cannot, however, have originated very early 
in the evolution of a species, and the observed phenomenon of their unduly 
precocious appearance and rapid development in the ontogeny requires additional 
explanation. In L. cratcegella, ostryoefoliella, lucidicostella, hageni and morrisella, 
these were the first dark markings to appear. The first tinge of gray appeared 
before the ground color itself had reached its adult shade or rarely even before 
it had reached its adult configuration. It is possible that physiological causes 
act directly toward this end. In the racial development, the segregation of 
black scales over a limited area and the later modification of these scales structur- 
ally has been accomplished gradually; the results have become permanent in 
the species, and the scales, when first formed before any pigment has entered 
them, have a structure identical with that acquired late in phylogenetic develop- 
ment. It is suggested, in explanation of the phenomenon of the early appearance 
of black pigment in them, that the concentration of pigment-forming substances 
within a smaller space — the interior of these smaller scales — results in a more 
intense chemical action over a locahzed area and thus hastens development. 

The general conclusions which have been drawn from the study of pupal 
development may be summarized as follows : 

1. The primitive type of color pattern consists of a series of seven trans- 
verse bands, which, except the first, cross the wing perpendicular to the costal 
margin and are not wider than the unpigmented fasciae between them. Their 
positions are determined by the course of the longitudinal nervures. 

2. In the evolution of the genus, changes in extent alone of bands are 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 149 

brought about by the uniform spreading of the pigment toward the base, the 
edges of the bands remaining straight. Changes in the extent and form of these 
bands have taken place through the action of any or all of the three following 
dynamic processes : (a) The middle portion of a band may be produced distally 
until it comes in contact with the band beyond it. (b) The extremities of a 
band may be broadened by being produced proximally. (c) The extremities 
of a band may be narrowed by the retraction of pigment from their outer edges. 
The action of the first two may be observed directly, the third is an inference 
from a comparison of adult markings. 

3. The bands, either in their primitive shape or as modified through the 
course of evolution, constitute the ground color upon which a second darker 
series of transverse characters is superimposed. These are properly termed the 
markings and appear at the limits between ground color and unpigmented areas. 
Their relative time of appearance, ontogenetically, is dependent upon the time 
when that portion of the edge of a band has become fixed phylogenetically. 

4. Later in the ph3dogenetic history, spots and longitudinal black markings 
may appear. For reasons not fully understood, certain of these markings appear 
earliest in the ontogeny. 

5. Recapitulation in the ontogeny is at most only partial and is confined 
to those species or to those parts of the wings in which there has been the least 
advance from a primitive condition. Here also a distinction must be made 
between ground color and markings. 

(e) Phylogenetic Development of the Color Pattern. 

From the previous discussion, it was seen that a few definite processes, 
identical in all of the species, have acted to produce modifications in the extent 
and configuration of the areas of ground color. Later, a set of darker transverse 
markings has been superimposed upon the ground color. The dark pigment 
appears in rows of scales contiguous to unpigmented areas. There are two 
possibilities in regard to the place of its first appearance, namely, the outer or 
the inner edge of a band. 

While the evolution of the pattern of the ground color has taken place in 
the same directions in both divisions and in the two subgenera of the genus, 
the development of the dark markings has followed different directions. In the 
division whose larvse are of the ordinary cylindrical type and in Porphyrosela, 
the dark markings appeared first on the outer edges of the bands: in the division 
whose larv2e are of the modified flat type and in Cremastobombycia, the margins 
appeared first on the inner edges of the bands. 

Two different inherent tendencies in development are therefore exhibited. 
These two lines of development must have diverged early in the phylogeny, 
while the only color pattern was still that blocked out on the white wing by the 
shape of the areas of ground color and before any of the dark markings had 
appeared, since neither type of marking can be derived from the other, and the 



150 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

species of the first division are more closely related among themselves than to 
any of the species of the second division or of Cremastobomhycia. 

An ancestral form, more primitive in respect to generic structure as well as 
color pattern and transversely marked with seven bands of a uniform pale 
yellowish color, has evidently given rise first to a series of species in which dark 
margins have developed earliest on the outer edges of bands — in this case, the 
white streaks and fasciae are said to be internally dark margined. Later, or 
perhaps contemporaneously, in another species of the same ancestral strain, 
the opposite tendency has developed, and there has been evolved a series of 
species in which dark margins appear earliest on the inner edges of the bands — 
in this case, the white streaks and fasciae are said to be externally dark margined. 
A few of these latter species, constituting the subgenus Cremastobombycia, have 
retained a more primitive generic structure; the remainder have followed the 
same course of evolution structurally as the species of the first division of the 
genus. It is, of course, possible that this second tendency originated twice 
and independently. 

Several factors combine to render it probable that Cremastobombycia (in 
its modern form) and the ''flat-larval group'' originated at a somewhat later 
period than the typical LithocoUetis (Fig. 26). The restricted geographical 
range of the ''flat-larval group'' and of Cremastobombycia, which with one 
exception are confined to America, indicates their comparatively recent origin. 
Considerations based upon larval characters confirm this view. The later larval 
stages of the typical LithocoUetis are identical with those of Gracilaria, which is 
without question accepted as the ancestor of all these groups. The corresponding 
stages in the larva of Cremastobombycia have a more flattened and triangular- 
shaped head, without, however, the structural modifications which have de- 
veloped in the "flat-larval group." It may be concluded, then, with reasonable 
certainty, that after the origin of the typical LithocoUetis, the species of the 
ancestral stock retained for a short period their imaginal structure. During 
this time, changes in the larval form were initiated. In the ancestral form of 
Cremastobombycia, development along this line did not progress far, and the 
larvse have preserved the normal mode of feeding; hence there has been no 
attendant structural modification. 

Cremastobombycia may have originated after a certain amount of evolution 
in the color pattern had already taken place; this view is supported by the 
observation that none of its species conserves as primitive a type of marking as 
is to be found in several species of the "flat-larval group." 

We may conclude, therefore, that the immediate ancestor of all the groups 
under discussion was of a somewhat more primitive structure than Cremasto- 
bombycia as we now know it. The structural relations of the four groups with 
reference to the ancestral stem are illustrated diagrammatically by Fig. 25; the 
relative time of origin of each by Fig. 26. The similarity of the color pattern of 
the species of Cremastobombycia to that of some of the species of the second 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 151 

division of the genus does not in any way indicate that this is primitive; it has 
rather been produced independently in the two groups, by the action of the 
same three fundamental factors. 

The phylogenetic tree thus shows two main stems extending in different 
directions from a common origin. By the application of the three general 
principles directing the evolution of the pattern of the ground color, it is possible 



seta 



fitkocclletis Tlat'larval 



fvrphurosela ^^ 




; S 




; ^ 


TUt -Ureal 


MkoJleU^ 1 


^roup. 


Jypical ^ 




'\ ^ 


/' 



. LreTnastohomhycia 



Cl-ncestral /orm, 

Fig. 25. Phylogenetic tree showing structural rela- 
tionships of the groups of Lithocolletis . 



Clncestral Tcrrw. 

Fig. 26. Phylogenetic tree showing relative time of 
origin of the groups of Lithocolletis. 



to retrace the steps in the origin of the different groups of species. The evo- 
lution of the species of the ''cylindrical-larval group/' which will be discussed 
first, is illustrated on Plate III. 

In all of the species except hataviella (Fig. 58), there has been a fusion 
of Bands I and II along the costa. 

If evolution in the shape of Bands II and III has been in the same direction 
and at the same rate, and the outward growth of the middle of each has not 
been sufficient to bring it in contact with the band following, and this outward 
growth has been compensated for by an equal growth toward the base of the 
extremities of Bands III and IV, species characterized by two entire fasciae will 
be produced, the first at the basal fourth, the second at the middle of the wing. 

Where evolution ceases early, all or most of the bands may be preserved as 
transverse bands. L. tiliacella (Fig. 1) has been differentiated as a species 
when, except for the fusion of I and II on the costa. Band IV alone had come 
in contact with the band beyond. Specific differentiation, that is, the production 
of dark margins, etc., has also halted soon, as we observe that no dark scales 
are present on the last three bands. If development along the same line proceeds 
farther, and by the farther outward growth of the middles of Bands II and III 
and the extension inwardly of the extremities of III and IV, the fascise between 
them become distinctly bent, the pattern of the ground color resembles that of 
oregonensis. There has also been an accompanying gradual deepening of the 
ground color. Specific differentiation at this level over a long period, as evi- 
denced by the black apical spot, has given rise to oregonensis (Fig. 2). If, 
on the other hand, evolution of the first three bands stops at the level of tiliacella 
but continues in the apical four bands until IV, V, VI and VII are continuous 
along the middle of the wing, species of the type of the European L. nicellii will 
be produced. 



152 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

If the bands continue to become more and more bent outwardly and the 
fascise between them gradually narrowed, forms of the type of fragilella (Fig. 3) 
will be produced. If now the action of the third law comes into play, the 
outer edges of the bands on the margins will move toward the base; if the 
extremities of the bands are extended toward the base at the same rate, very 
acutely angled fascise will result, as in celtifoliella (Fig. 4) . 

If the extension of the ground color toward the base in Band VI has taken 
place rapidly, there is an entire obliteration of white between V and VI, which 
then form a single uniformly colored band. In tritcenianella (Fig. 5), affinis 
(Fig. 6) and ostensackenella (Fig. 7), this has occurred, Bands II, III and 
IV remaining nearly straight. In mariceella (Fig. 8), these bands have 
become bent outwardly. In ostensackenella, while the bands have remained 
straight, there has been a very decided advance and specialization in other 
directions; namely, in the structural modification of the scales forming the 
fascise and spots and in the darkening of the base of the wing into a deep brown 
except near the base of the dorsum. There has also been considerable modi- 
fication in the larva, which has become more flattened and in which the sides 
of the segments project more prominently than usual. It also deviates from 
the typical habits of the genus in that it leaves the mine to pupate. 

We may regard Porphyrosela as having originated from an ancestor with 
this type of marking. The recent origin of the species within it (Fig. 9) is 
indicated by the deep ground color, dark margins on either side of the white 
fascise and the structural modification of the white and the purple scales. 

If the extension distally of each of the bands along the cell has continued 
until it has reached the band beyond and the inner extremities of the bands 
have been produced basally at a slower rate, the result is the production of pairs 
of opposite white streaks. 

In auTonitens (Fig. 10), it is probable that the fascise were considerably 
narrowed before these processes began, thus accounting for the almost per- 
pendicular position of the white streaks. 

In the remaining groups of species, these processes began early and the 
pairs of streaks are more or less oblique. There is first produced a form in 
which the ground color is blocked out as in argentinotella (Fig. 11). Occi- 
tanica (Fig. 12) is derived from argentinotella by the obliteration of the first, 
fourth and fifth costal streaks. 

If now a movement of the extremities of each band toward the base is 
accompanied by a corresponding extension of the extremities of the band beyond 
it toward the base, very obhque white streaks result. Where these movements 
have taken place at an approximately equal rate in all of the bands, forms such 
as leucothorax (Fig. 13) will be produced. The outer edge of Band II on the 
costa has been retracted completely to the base so that the first white costal 
streak begins at the base. This species furnishes further evidence of the long 
continuance of evolution by the well developed apical spot. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 153 

If on the dorsal margin^ the retraction of pigment from the outer edge of 
Band III takes place more rapidly than the extension proximally of the extremity 
of that band, its dorsal portion will disappear, and the second white dorsal 
streak will coalesce with the first; fitchella (Fig. 14) typifies this result. The 
extension of color onto a white streak has probably taken place most rapidly 
just within the dorsal margin; the evidence for this conclusion rests upon the 
observed concavity of the outer edges of the white streaks and their greater 
width on the margin. 

If the most rapid movement, as is usually the case, has been that of the outer 
edge of Band II toward the base, the first result will be the union of the upper 
inner edge of the first white dorsal streak with the short oblique streak at the 
base separating Bands I and 11. A small streak of ground color will be left 
between them on the dorsum; this soon becomes a small spot removed from 
the dorsal margin by the more rapid shrinking away of Band II on the margin. 
Salicifoliella (Fig. 15) and tremidoidiella (Fig. 16) have been differentiated as 
species at this level. 

The small spot of ground color just referred to becomes smaller and smaller 
and finally disappears. The base of the dorsal margin is then occupied by a 
white patch whose outer edge is the inner edge of Band III. Differentiation at 
this stage has given rise to hageni (Fig. 17), arhutusella (Fig. 18) and insignis 
(one variety) (Fig. 19). In hageni and insignis, the first white costal streak 
has disappeared entirely. Following closely behind the retraction of pigment 
from the outer edge of Band II on the costa, the extremity of Band III has 
been produced along the costa to the base; phylogenetically then, this is the 
second time pigment has appeared along the base of the costa. In arhutusella 
(Fig. 17) the first costal streak has been involved in a change similar to 
that of the first dorsal with which it has united. In these three species equally 
distinct dark margins have appeared on either side of the white streaks, and 
there has been a very decided darkening of the scales of the ground color between 
the streaks, indicating that after the general phylogenetic evolution of the 
pattern of the ground color had come to a standstill, specific differentiation pro- 
ceeded rapidly and for a considerable period of time. In the other variety of 
insignis (Fig. 20), Band III in its dorsal half has been produced to the 
base, most rapidly just above the dorsum, leaving a white median basal streak 
and a white spot on the dorsum near the base. This then is the method by which 
a median long basal streak has originated; its basal part is therefore homologous 
with the white streak separating Bands I and II; its apical half is homologous 
with a part of the white streak separating the dorsal portions of Bands II and III. 

Where the extension of Band III to the base has followed immediately on 
the progressive withdrawal of pigment from the outer edge of Band II, without 
the intervening cessation in development found in insignis, the configuration of 
the color areas is that of the group of species of which obscuricostella (Fig. 25) 
and cratcegella (Fig. 36) are typical examples. In most of the species of this 



154 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

group, there has also been a retraction of pigment from the outer edge of 
Band III, and at the same time, the extremities of Band IV have been produced 
toward the base so that the first pair of white streaks are very obhque and are 
situated before the tip of vein 16 which in more primitive forms determines the 
position of these white marks. The obhteration of the first white costal streak 
has not been attained in all the forms which reached this level before evolution 
in the pattern of the ground color halted and species differentiation began, 
since it is preserved in some species and lost in others. 

Within this group the development of the dark markings in the apex has 
taken two different directions; the black marking in the apex may take the form 
of a round apical dot, or of a streak or patch of black scales of variable shape. 
Of the species with apical dots, carycealhella (Fig. 21) lags somewhat behind the 
other species; the suffusion of the base of the wing with pale yellow is not 
yet complete, but the first costal streak has been lost. Development has been 
more rapid toward the costa than in the dorsal half of the wing; the converse is 
true for rileyella (Fig. 22) where the first white costal streak remains. In 
conformity with the principle that within a group a darker ground color and the 
presence of dark markings indicate a higher phylogenetic position, the sequence 
of the remaining species with an apical dot will be ostrycefolieUa (Fig. 23), 
olivceformis (Fig. 24), ohscuricostella (Fig. 25) and kearfottella (Fig. 26). In the 
last two species all trace of a white spot near the base of the dorsum has 
vanished. 

Of the species characterized by more or less irregular patches of black scales 
in the apex, populiella (Fig. 27) is probably the most primitive from the point 
of view both of color areas and markings. Among several of the species, 
namely, diaphanella (Fig. 28), salicivorella (Fig. 29), deceptusella (Fig. 30), alni 
(Fig. 31) and alnicolella (Fig. 32), the pair of streaks in the middle of the wing 
are not very oblique, that is, there has been a more restricted action of the last 
two of the three processes of evolution than is observed in the five following 
species. In ledella (Fig. 33), incanella (Fig. 34), scudderella (Fig. 35), cratcegella 
(Fig. 36), malimalifoliella (Fig. 37) and propinquinella (Fig. 38), these streaks 
are very oblique. 

If evolution of the pattern of the ground color, instead of halting at the 
level of the preceding group of species, proceeds farther, it takes place in two 
directions. 

1. The base of the wing may be uniformly suffused with ground color, so 
that no white streaks remain when evolution ceases, and therefore no dark 
markings develop. The configuration of the ground color in the remainder of 
the wing has remained constant during these changes. This is the condition of 
affairs in sexnotella (Fig. 39), ceriferella (Fig. 40) and obsoleta (Fig. 41). In ohsoleta 
the pattern remained fixed for a short time, and the development of dark pig- 
ment in the scales adjacent to the white streaks was initiated, then the exten- 
sion of all the bands toward the base was resumed, checking further develop- 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 155 

ment of dark pigment. The result is a tendency toward a uniform distribution 
of ground color over the entire wing. 

It may be objected that the color pattern of the three species just discussed 
could have been derived directly and in a more simple manner from that of 
L. argentinotella (Fig. 11) by the broadening of the extremities of Bands 
II and III toward the base, resulting in the obliteration of the white streaks 
separating Band I from II and Band II from III. On this hypothesis the 
greater changes have occurred in the middle of the wing since the oblique pair 
of streaks in the middle of the wing have been produced by the combined action 
of the second and third processes of evolution. This is not in agreement with the 
facts observed up to this stage in the evolution of the color pattern, namely, 
that the greatest changes have occurred near the base of the wing, nor with the 
general principle that development is more rapid in the more proximal parts 
of an organism. 

2. The shrinking away of the ground color at the extremities of the bands 
may continue and the outer edges of Band III may be involved to a greater 
extent than hitherto observed. In albanotella (Fig. 42) evolution in this 
direction has ceased comparatively early, the darker ground color and heavier 
dark margins indicating the longer time occupied in specific differentiation. 
In argentifimhriella (Fig. 43) the withdrawal of color from the base of 
the wing has been almost complete and there has been no later extension of 
color toward the base from Band IV. In lucidicostella (Fig. 44) there is a 
slight extension of color along the dorsal margin; the halting in development has 
been too recent for a dark line of scales to develop on the streak of ground color 
extending along the upper side of the cell. In clemensella (Fig. 45) this 
streak has also disappeared. In the four preceding species, evolution has taken 
place more rapidly on the dorsal than on the costal margin of the wing. In 
quercialbella (Fig. 46) and trinotella (Fig. 47) the costal half of Band III 
has also shrunk away; the only transverse bands then remaining are the 
four apical ones. In the European fauna, the final consummation of this process 
is witnessed in such species as L. cramerella and L. tenella. Development has 
halted at different levels, as in our species, and dark streaks have appeared at 
the edges of the bands. Gradually then bands more and more distal have 
shrunk away, leaving behind them the dark fuscous streaks on an almost white 
ground. 

In all of the groups whose evolution has been traced, modification in the 
shape of Bands II and III, in the early phases of evolution has progressed in the 
same direction and at approximately equal rates, so that the bands are of 
similar shape (cf. argentinotella, Fig. 11). 

In the following species evolution has proceeded independently in each of 
these bands. 

Changes may proceed very slowly on the inner edge of Band IV and outer 
edge of Band III; the tendency is then toward the preservation of a median 



156 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

white fascia. If the outward growth of Band II along the cell is comparatively 
rapid, a pair of opposite streaks will be produced at the basal fourth. These 
changes have taken place very early in the phylogenetic history, and if evolution 
of the pattern of the ground color ceases here, species of the type of morrisella 
(Fig. 48), uhlerella (Fig. 49) and rohiniella (Fig. 50) will develop. The 
laws governing specific differentiation have had an opportunity to operate 
over a long period of time, and very highly specialized individual characters 
have developed. In rohiniella evolution of the pattern did not cease quite as 
soon as in the other two species, the fascia has been narrowly separated into 
two streaks and all of the streaks have become more oblique. In consequence 
of the later beginning of specific differentiation, the individual characters are 
not as highly specialized as in uhlerella and morrisella. 

If the edges of the first pair of streaks move toward the base, and there is 
no corresponding extension of the extremities of Band III toward the base, 
species of the type of lucetiella (Fig. 51) will be produced. 

Where Band III has been extended to the base, there is a basal streak very 
similar to that of cratcegella (Fig. 36) and the other species of that group. 
Martiella (Fig. 52), gemmea (Fig. 53) and symphoricarpella (Fig. 54) have 
originated thus. In symphoricarpella the basal streak is very small — ^the ground 
color has shortened and narrowed it. 

If the outer edge of Band III instead of remaining straight has grown distally 
along the cell and at the same time the movement of its extremities toward the 
base has been accompanied by a compensating extension of the extremities of 
Band IV toward the base, angulated fasciae will result; apicinigrella (Figs. 
55a, 556) and celtisella (Fig. 56) have been thus differentiated. Finally 
this angulated fascia may become very acutely angled through the shrinking 
away of Band III and the white may be extended along the margins to the base 
of the wing. At this stage a very slight outward growth of the middle of Band III 
will divide the fascia into very oblique streaks; basistrigella (Fig. 57) has 
been thus produced. In this species the separation of a white fascia into a 
pair of streaks was the last step in evolution; in the other species characterized 
by opposite streaks, this process has been one of the earliest events in evolution. 

Bataviella (Fig. 58) is an early isolated offshoot from the main stem; 
it alone of all the species has preserved, in some of its varieties, Band I at the 
base of the wing distinctly separate from II. Specific differentiation has ex- 
tended over a length of time sufficient for all of the scales of the ground color 
to become dark tipped. 

The second main stem of the phylogenetic tree, which has given rise to 
Cremastohomhycia and the ^^flat-larval group," is illustrated on Plate IV. 

The species of Cremastohomhycia and of the ^^flat-larval group'' have fol- 
lowed very similar lines of development. In Cremastohomhycia the result has 
been modifled somewhat by the shorter and very oblique, almost horizontal 
position of the white streak separating Bands I and II. A white basal streak 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 157 

when formed is therefore nearer the dorsal margin. The chief forces acting in 
the evolution of the pattern in this subgenus are the more rapid growth distad 
of Band II as compared with Band III and the extension proximad of the ex- 
tremities of Bands III and IV. The sequence of the species is as follows: 
grindeliella (Figs. 59a, 5%), solidaginis (Fig. 60), ambrosiella (Fig. 61), 
ignota (Fig. 62), verbesinella (Fig. 63). Grindeliella shows the basal streak in 
actual process of formation; where the dorsal arm of the first fascia is wanting, 
the black scales at the tip of the basal streak are homologous with those 
on the outer margin of the fascia. All show the tendency which arises inde- 
pendently throughout the ^^flat-larval group'' also, toward the complete fusion 
of Bands V and VI. None of these species can be regarded as very primitive. 
The similarity to a group of species in the division of the genus shortly to be 
discussed is due to the fact that the same laws underlie their evolution. 

A tendency similar to that witnessed among several of the species of the 
first division of the genus, toward the preservation of Bands II and III in a shape 
approaching the primitive, prevails among many of the species of the second 
division of the genus. Obstrictella (Fig. 64) has preserved Bands II, III 
and IV in a very primitive condition; during its differentiation, however, the 
white streak at the base has been entirely obliterated. 

Above this level, evolution takes place in four divergent directions, as repre- 
sented on Plate IV. 

In one of these branches. Bands II, III and IV tend to remain separate. 
Within this group, the first step in evolution is the outward extension of the 
middle of Band IV to meet Band V; at the same time the bands become displaced 
very slightly toward the base of the dorsum; the fasciae between them are not 
as yet angulated. Specific differentiation at this level has produced tubiferella 
(Fig. 65), in which all white markings beyond the fasciae, except sometimes 
a minute white dot before the apex, have been suffused with ground color; 
aceriella (Fig. 66) and hamameliella (Fig. 67), the latter more advanced 
because of its deeper ground color; ostryarella (Fig. 68), corylisella (Fig. 69), 
cesculisella (Fig. 70) and guttifinitella (Fig. 71). The loss of the white 
streak at the base seems to be accomplished after the principal changes 
in the configuration of the ground color have been brought about, that is, 
after specific differentiation has set in. The fact that the white streak 
extends entirely across the wing, separating Bands I and II completely in 
such species as hamadryadella (Fig. 77) and umbellularice (Fig. 78) which are 
by no means primitive in regard to the shape of the areas of ground color, and 
observations on the development of color in the pupal wings of cesculisella, 
support this hypothesis. 

In carycefoliella (Fig. 72) and lentella (Fig. 73), the bands have become 
quite distinctly though obtusely angulated. 

Above this level evolution has taken divergent paths. In one direction, 
evolution in the shape of Bands II, III and IV has progressed in the same manner 



158 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

and at the same rate, so that although the fascise between them have become 
acutely angled, they have remained parallel. Macrocarpella (Fig. 74) and 
cmcinnatiella (Fig. 75) have been differentiated at this level. These two 
species are characterized by an unusual number of dark tipped scales; the 
fascise are also internally dark margined near the costa. In saccharella (Fig. 
76) evolution has continued farther, and other changes of a different char- 
acter have resulted. There has been a slight displacement of the dorsal obHque 
streaks toward the base; the first of these is brought into contact with the basal 
streak. The costal portion of the first fascia has been replaced by the ground 
color. 

In the other direction, where evolution has progressed at a more rapid rate 
on the outer edge of Band III and inner edge of Band IV, than on the outer and 
inner edges of Bands II and III respectively, the second fascia will be more 
acutely angled and its arms more obhque than the first fascia. Such is the 
condition in hamadryadella (Fig. 77), umbellularice (Fig. 78) and agrifoliella 
(Fig. 79). In the first of these there is but little divergence in direction 
of the two fascise, evolution in this direction having halted compara- 
tively early. Specific differentiation progressed rapidly and dark pigment 
developed along the outer as well as the inner edges of the bands. At this stage 
regressive changes have commenced; the bands have shrunk away toward the 
base, most rapidly at the extremities, but also in the middle, leaving behind them 
the Hues of dark scales which marked their former outer edges. In umbellularice 
and agrifoliella, progressive evolution continued longer, and the arms of the 
second fascia are very oblique compared with those of the first. Specific differ- 
entiation has continued longer in agrifoliella than in umbellularice; the recent 
disappearance of the white fascia separating Bands I and II is shown by the 
presence of black scales external to its normal position and by the occasional 
presence of a few pale scales anterior to them. 

In all of these species characterized by two white fascise, there is a tendency 
toward a disproportionate acceleration of the outward extension of the bands 
along the cell, with the attendant result that the fascise are often interrupted at 
the angle. 

In a collateral line of development, there has been an early acceleration in 
the processes of evolution affecting the outer edge of Band II and the inner 
edge of Band III. As a result Band II becomes fused with Band III over a 
considerable space in the middle of the wing, at a period when III and IV are 
still separated from one another by an angulated fascia. Fletcherella (Fig. 80), 
arcuella (Fig. 81), betulivora (Fig. 82), australisella (Fig. 83), bethunella (Fig. 84), 
chamber sella (Fig. 85), cervina (Fig. 86), platanoidiella (Fig. 87), castaneceella 
(Fig. 88) and fasciella (Fig. 89) have followed this path of evolution. Chamber- 
sella (Fig. 85), cervina (Fig. 86) and platanoidiella (Fig. 87) have been differ- 
entiated subsequent to the first five species; fusion of Bands II and III has been 
complete in the dorsal half of the wing. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 159 

In castanemella (Fig. 88) and fasciella (Fig. 89), evolution has progressed 
more slowly on the outer edge of Band III and inner edge of Band IV; the 
median fascia remains almost straight, but the other white markings have 
almost disappeared. 

In two species, nemoris (Fig. 90) and gauUheriella (Fig. 91), the relations 
between the progressive changes in Bands II and III have been reversed. The 
tendency here is toward a fusion of Bands III and IV earlier than II and III, 
with the result that the second fascia is separated into opposite spots earher than 
the first. GauUheriella is the more advanced of these two species. 

In all of the groups whose evolution has just been traced, the action of the 
third process of evolution, namely, the retraction of pigment from the outer 
edges of the extremities of bands, has been of minor importance. In the evo- 
lution of four species, mediodor sella (Fig. 92), quercivorella (Fig. 93), conglomer- 
atella (Fig. 94) and ulmella (Fig. 95), the characteristic longitudinal white streak 
has originated through the action of this process at the extreme dorsal end of 
each of Bands II, III and IV in sequence, followed by the extension of color 
toward the base from Bands III and IV, just within the dorsal margin. This is 
analagous to the process which has occurred in species of the first division of 
the genus, where it was observed that the most rapid extension of a band into 
the white streak preceding it took place just within the margin. These processes 
occur first near the base, then the bands more and more distad are involved. 
In mediodor sella (Fig. 92) Band IV has not yet been produced toward the base 
to obliterate the dorsal arm of the median fascia; in quercivorella (Fig. 93) this 
advance has been made. In conglomeratella (Fig. 94) and ulmella (Fig. 95), the 
regressive changes have been extended to Band IV, which has shrunk away on the 
margin, allowing the white obhque streak to move proximally along the margin 
until it has united with the more proximal portion of the longitudinal streak. 
This theory of the origin of the longitudinal dorso-basal white streak is sub- 
stantiated by the variations in its width. It is widest at points correspond- 
ing to the original extremities of the white fasciae, and narrowest immediately 
behind them. 

From the foregoing account of the evolution of the groups and species of 
Lithocolletis, it is evident that the general evolution of the pattern of the ground 
color may halt at any level and the species differentiated at this level constitute 
a natural group of species more closely related to one another than to any other 
species. The level at which evolution has come to a standstill is no absolute 
criterion of the age of the individual species within a group. A species with but 
few specialized specific characters in a group whose color pattern marks it as of 
recent origin may be older phylogenetically than one of a more primitive group, 
where the high degree of specific differentiation attained marks it as of recent 
origin. It is to be expected that the most highly differentiated species, that is, 
those where the darker colors predominate both as regards ground color and 
markings, would be found in groups where the pattern of the ground color has a 



160 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

less degree of modification; the earlier evolution in this direction has halted, the 
longer will have been the time available for specific differentiation. On the 
other hand, species belonging to groups recently estabhshed and hence of high 
phylogenetic position, may be almost lacking in the darker colors. Actual 
examples of each of these possibilities are furnished among our species; morrisella 
(Fig. 48, PL III) and fragilella (Fig. 3, PL III) are examples of the first, quercial- 
bella (Fig. 46, PL III) of the second possibility. 

III. GENERAL DISCUSSION. 

Ontogenetic and phylogenetic studies upon the development of the color 
pattern in LithocoUetis lead to the conclusion that evolution has taken place in 
definite directions under the action of a few definite laws; in other words, that it 
has been orthogenetic. It was shown that the primitive color pattern, the first 
to be laid down upon the white wing, is a series of seven uniformly colored, pale 
yellow transverse bands. From these, the color areas, which form the ground 
color of the various groups of species, have been derived. The first tendency 
observed is a uniform widening of the bands. Evolution in the shape and extent 
of the primitive bands of ground color, as has been shown (see page 141), has been 
brought about by three definite processes, two of which were observed in actual 
operation in the development of color in the pupal wings; the third is a necessary 
inference from the lack of agreement between the primitive positions of the bands 
and their positions in the more advanced species. The most far-reaching and 
widespread changes have taken place toward the base of the wing proximal to 
the transverse vein. 

The final result of the action of these three processes is a uniform ground 
color; this uniformity will be attained first near the base of the wing, since it is 
here that evolution has proceeded most rapidly. The color bands in the apical 
half of the wing, which were laid down later, are modified at a slower rate and 
retain more nearly their primitive shape. These observations are in agreement 
with the general principle that development is more rapid in the anterior and 
proximal parts of an organism. 

The observed evolution in the pattern of the ground color suggests that 
the uniform yellowish ground color which suffuses the wing in the higher Lepidoptera, 
beginning at the base and spreading distalward, is the outcome of a phylogenetically 
older type of marking, originally banded, and later fused to a uniform color, and 
that the markings are a second series superimposed upon the first. 

If the disposal of the transverse primitive bands of ground color is de- 
pendent upon the positions of the nervures, as my observations on LithocoUetis 
have indicated, then in the primitive color pattern of the ancestral Lepidoptera 
where more veins are present and their arrangement on the margins is more 
symmetrical, the number of these bands should be considerably augmented. 
As evolution has proceeded, this primitive type of color pattern would have been 
modified in various ways. Attendant upon the degradation in venation in some 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 161 

of the lower groups, there must have been immediate and complete fusion of 
bands occupying adjacent interspaces, when the vein which separated them was 
lost. Modification in the shape of the wings, resulting in changes in the relative 
positions of the nervures, must also have been an important factor in producing 
correlated changes in the primitive color pattern by bringing about displacement 
and fusion of some of the bands. Just what modifications in the color pattern 
would have been produced by the direct action of these conditions, could only 
be determined by a complete knowledge of the actual series of changes which 
have taken place in the wings of Lepidoptera. Beyond, and apparently inde- 
pendent of these factors, there is the evolution in the shape and extent of the 
color areas themselves. 

It was found that dark markings, properly so-called, appeared at the limits 
between ground color and unpigmented areas. Increase in breadth of a dark 
marking takes place away from an unpigmented area. The dark markings do 
not appear until the edge of a color area has remained constant for an appreci- 
able length of time. Since they appear at the edges of color areas, their shape 
and position are in great part determined by the same laws which control the 
evolution of the pattern of the ground color. Markings once formed tend to 
become permanent and immovable. Thus we find that the suffusion of an un- 
pigmented area with ground color subsequent to the formation of a dark streak 
does not affect its permanency; the shrinking away of ground color leaves a dark 
streak or line isolated in an otherwise unpigmented area. Therefore, although, 
during the early stages of evolution, the development of markings was entirely de- 
pendent on the configuration of the ground color, these markings once permanently 
established in the race, tend to reappear independently of the ground color. When 
this level has been reached in racial history, we have a series of transverse markings 
appearing on a uniform ground color. This is the condition in all of the higher 
Lepidoptera. In the ontogeny of such groups, there is no evidence to show that 
these markings are a second series superimposed upon the earlier primitive one. 

If the theory of the origin of dark markings on opposite edges of primitive 
bands of ground color is a valid one, we should expect to find in the higher types, 
that there is a tendency for dark stripes to recur in pairs, and that fusions at any 
single period would be more apt to occur between any two consecutive stripes 
than between three consecutive stripes. Observations confirm this hypothesis. 
Among many of the Pyralids, the dark markings are formed of two dark lines 
connected by a paler color; each of these marks is separated from a similar pair 
of lines by ground color. Even in the butterflies, the tendency toward grouping 
of dark marks in pairs is witnessed. Elmer's ('97) series of adult forms of Papilio 
and von Linden's ('98, '02) figures of the pupal development illustrate this 
principle. In the pupal development of the wings of Papilio machaon, the 
tendency for the dark scales to appear first at the edges of bands was noted; 
bands thus formed have, on my hypothesis, originated from the fusion of dark 
stripes situated on either side of a primitive band. 



162 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

The great diversity to be observed in the position^ shape and extent of the 
dark markings in the various groups of Lepidoptera, is due to differences in the 
direction of evolution of the pattern of the ground color, and the different levels 
at which it has halted, permitting the dark markings to develop. 

The actual appearance of dark pigment in certain defined positions is prob- 
ably due to physiological factors; just why these processes should occur con- 
tiguous to unpigmented areas is largely a matter of conjecture. It is possible 
that the chemical changes involved are oxidative in their nature; the presence 
of air in the unpigmented hollow scales may possibly accelerate chemical proc- 
esses along this line. This supposition will however not account for the phylo- 
genetic permanency of such markings after the ground color covers the wing 
uniformly. 

The investigations of previous workers upon the color patterns of Lepi- 
doptera have been limited to the markings, that is, to that series which I have 
designated as secondary and superimposed upon an original primary color 
pattern. In as much, however, as these markings have originally been deter- 
mined by the configuration of the pattern of the ground color, the laws con- 
cerning their places of appearance should agree with my observations on the 
evolution of the pattern of the ground color; it is on the contrary not to be 
expected that these laws concerning behavior of the markings will apply in their 
entirety to the comparatively primitive and phylogenetically older type of 
markings in this genus. The laws governing the color pattern have been based 
upon more highly developed markings often of comparatively recent origin 
phylogenetically. For convenience in comparison a statement of some of these 
laws of coloration follows. The following are those advanced by Mayer ('97) : 

^^(a) Any spot found upon the wings of a moth or butterfly tends to be 
bilaterally symmetrical, both as regards form and color, the axis of symmetry 
being a line passing through the center of the interspace in which the spot is 
found, and parallel to the direction of the longitudinal nervures. (b) Spots 
tend to appear not in one interspace only, but as a row occupying homologous 
places in successive interspaces. Indeed we almost always find spots arranged 
in linear series, each similar in shape and color to the others and occupying the 
center of its interspace, (c) It is interesting to notice that bands of color are 
often made by the fusion of a row of adjacent spots; and conversely, chains of 
spots are often formed by the breaking up of bands, leaving a row of spots 
occupying the interspaces, {d) The most common method of disappearance 
is a shrinking away of the band at one end. It is very common to find bands 
shrinking away at one end. This is a special case of Bateson's law that the ends 
of a linear series are more variable than the middle. Sometimes however they 
shrink away at both ends, and very often, they break up into a row of spots, 
which may then contract into the centers of their interspaces and finally dis- 
appear. It is worthy of note that it is very rare to find a band breaking at the 
middle of its length and each half receding from the other, (e) The position of 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 163 

spots which are situated near the edge of the wing is largely controlled by the 
wing-folds or creases." 

Eimer has derived the various types of coloration from a series of transverse 
stripes (termed by him longitudinal because parallel to the longitudinal axis 
of the body) which break up into spots which fuse crosswise to form markings 
parallel to the longitudinal nervures, and finahy fuse to a uniform color. New 
markings appear on the body of the animal from behind forwards and from above 
downwards, or conversely, whilst the old ones disappear in the same direction 
and succession. 

I have shown that the ground color has been derived from a series of such 
transverse elements; conversion into a uniform color has taken place directly 
by an extension of color onto previously unpigmented areas, distad through the 
middle of the wing in the ceh, proximad on the margins. The positions of the 
markings are arbitrarily determined. They are dependent upon the level at 
which evolution in the pattern of the ground color acting in a few definite direc- 
tions has come to a standstill. The actual appearance of the markings is prob- 
ably due to physiological activities whose nature is not understood. The first 
markings are usually transverse, rarely longitudinal when the modification 
in the ground color has been far-reaching. These transverse markings are in 
the nature of narrow lines or streaks, phylogenetically the forerunners of the 
bands of higher Lepidoptera. Since the streaks and lines of dark scales in Litho- 
colletis still retain their primitive condition as originally laid down, it is not to he 
expected that the laws which Mayer has given, based upon the transformation of 
spots and bands in the higher Lepidoptera, would find wide application in this 
group. Portions of a pair of such streaks in Lithocolletis will be found at the 
margins and in each interspace which the band from which they are derived 
crosses. Breaking up of bands formed by the growing together of these streaks 
will result in conditions such as Mayer has described for spots and series of spots. 
Any spot such as the apical spot is bilaterally symmetrical and occupies the 
center of its interspace. The primitive bands from which the ground color has 
been derived and which have been regarded as a primary set of markings upon 
which a second set, the markings proper, have been superimposed, have exhibited 
the tendency toward shrinking away at each end. 

The ultimate causes which determine the definitive positions of the primitive 
bands are unknown. Von Linden has found that in the lower orders of insects, 
the coloring matter has a tendency to collect on transverse veins; this however 
does not bring us any nearer to a real explanation of the phenomenon of colora- 
tion. The probability that the origin of the markings, which appear secondarily, 
may be traced directly to physiological factors, renders it reasonable that the 
appearance of the primary series is conditioned by like physiological and morpho- 
logical factors within the organism itself and is independent of external factors. 

Evolution in the pattern of the primitive series of bands has been shown to 
have taken place in a few definite directions; the diverse patterns which have 



164 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

been produced are the result of different combinations of three general processes 
already discussed. 

IV. SUMMARY. 

Observations on the development of color in the pupal wings and a com- 
parison of the color pattern in adult forms of Lithocolletis have shown that in 
his group the primitive color pattern is a series of seven uniformly colored pale^ 
yellow transverse bands, separated from one another by unpigmented areas. 
The disposal of these bands is dependent upon the course of the longitudinal 
nervures, since the points of origin or the tips of the veins mark the positions of 
the unpigmented fasciae between the bands. 

From this primitive color pattern, the several different types of color pattern 
in this genus have been derived. Evolution has taken place in definite direc- 
tions, under the action of three general processes, which were found to be suf- 
ficient to explain the origin of the different color patterns. These processes have 
been stated thus: (a) The middle portion of a band may be produced distally 
until it comes in contact with the band beyond it. (6) The extremities of a 
band may be broadened by being produced proximally. (c) The extremities 
of a band may be narrowed by the retraction of pigment from their outer edges. 
The particular result in any case, that is, the configuration of the color areas, 
is due to the manner and extent of the action of these processes. 

During pupal development, these phylogenetic changes are repeated only 
to a very limited extent; recapitulation is confined to those species or to those 
portions of the wing in which there has been the least modification of the primi- 
tive transversely banded type of marking. 

These bands either in their primitive or modified shape, constitute the 
ground color. Upon this ground color, a second darker series of elements, the 
markings proper, also usually transverse, are superimposed. The different levels 
at which evolution in the pattern of the ground color has halted, that is, the 
configuration of the areas of ground color, are the important factors in deter- 
mining the phylogenetic sequence of large groups; the particular colors and the 
markings determine the positions of the species within those groups. 

These markings appear at the limits between ground color and unpigmented 
areas, as one or more lines of dark scales along the edge of a band adjacent to a 
white fascia or streak. Their appearance then is probably due to physiological 
factors within the organism itself, and is independent of external conditions. 
In the ontogeny, the relative time of appearance of the dark margin of any band 
is dependent upon the time when the edge of that band became fixed in the 
phylogeny. Before dark margins can develop, the edge of a band must have 
remained fixed for an appreciable time. Hence, where bands have been laid 
down late or have reached their present configuration late in racial development, 
the dark margin will develop at a correspondingly late period in ontogenetic 
development. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 165 

This principle holds good irrespective of whether or not there is a recapitu- 
lation of phylogenetic changes in the configuration of the color areas during 
pupal development. Therefore in the second and more recent set of characters, 
there is an actual recapitulation. A dark marking once permanently established 
in the race tends to reappear independently of the ground color, so that later 
suffusion of the unpigmented area contiguous to it with ground color, or the 
shrinking away of the ground color, does not affect its permanency. 

Later in phylogenetic history, additional dark markings, other than those 
contiguous to unpigmented areas, may appear. The development of these 
characters in the pupa becomes much abridged, and concomitant with this, 
their time of appearance is pushed back into the earlier stages of pupal develop- 
ment, so that they may appear simultaneously with or even earlier than char- 
acters which are much older phylogenetically. However, only those characters 
permanently established and of long standing in a species exhibit this precocity 
of development; recently acquired or variable characters appear ontogenetically 
in the order of their phylogenetic sequence. Where certain characters appear 
unduly early in pupal development, physiological factors probably act directly 
in bringing about this result. 

From a study of the phylogeny of the various groups of species, through 
the application of the processes of evolution already enumerated, it was found 
that the most far-reaching and widespread changes have taken place toward 
the base of the wing, proximal to the transverse vein. The final result is the 
production of a uniform ground color which will be attained earliest near the 
base of the wing where evolution has proceeded most rapidly. 

This observed evolution in the pattern of the ground color suggests that 
the uniform yellowish ground color which suffuses the wing in the higher Lepi- 
doptera, beginning at the base and spreading distalward, is the outcome of a 
phylogenetically older type of marking, originally banded, and later fused to a 
uniform color, and that the markings are a second series superimposed upon 
the first. 

The observations made clearly point to the conclusion that the evolution 
of the color pattern in Lithocolletis has been orthogenetic. 



166 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 

LITERATURE CITED. 

BeMMELEN, J. F. VAN 

1889. Ueber die Entwickelung der Fiirben und Adern auf den Schmetterlingsflligeln. Tijdsch. der 
Nederland. Dierkundige Vereeniging, Ser. 2, Deel 2, pp. 235-247. 

Braun, Annette F. 

1908. Revision of the North American Species of the Genus Lithocolletis Hiibner. Trans. Am. Ent. 

Soc, vol. XXXIV, pp. 269-357, 5 pis. 

1909. Phylogeny of the Lithocolletid Group. The Canadian Entomologist, vol. XLI, pp. 419-423. 

Chapman^ T. A. 

1902. The Classification of Gracilaria and Allied Genera. The Entomologist, vol. XXXV, pp. 81-88, 
138-142, 159-164. 

DlMMOCK^ G. 

1883. Scales of Coleoptera. Psyche, vol. IV, pp. 1-11, 23-27, 43-47, 63-71 

EiMER, G. H. T. 

1897. On Orthogenesis and the Impotence of N^atural Selection in Species-Formation. An address 

delivered at the Leyden Congress of Zoologists, Sept. 19, 1895. 55 pp. The Open Court 
Pubhshing Co., Chicago, 1898. 

Haase, E. 

1893. Untersuchungen iiber die Mimicry auf Grundlage eines natiirhchen Systems der Papilioniden. 

Bibliotheca Zoologica, Heft 8, Theil 1, 120 pp., 6 Taf. 
1893a. Untersuchungen liber die Mimicry auf Grundlage eines natlirlichen Systems der Papihoniden. 

Bib. Zool., Heft 8, Th. 2, 161 pp., 8 Taf. Enghsh translation by C. M. Child. Stuttgart, 

1896, 154 pp., 8 pis. 

Linden, M. von 

1898. Untersuchungen iiber die Entwickelung der Zeichnung des Schmetterlingsfliigeln in der Puppe. 

Zeitschr. fiir Wiss. Zool., Bd. LXV, pp. 1-49, pis. I-III. 
1902. Le dessin des ailes des Lepidopteres, reserches sur son evolution dans I'ontogenese at la phylo- 
genese des especes, son origine et sa valeur systematique. Annales des Sci. Nat., vol. XIV, 
pp. 1-196, pis. I-XX. 

Mayer, A. G. 

1896. The Development of the Win'g Scales and their Pigment in Butterflies and Moths. Bull. Mus. 

Comp. Zool, vol. XXIX, No. 5, pp. 209-235, 7 pis. 

1897. On the Colors and Color Patterns of Moths and Butterflies. Proc. Bost. Soc. Nat. Hist., vol. 

XXVII, No. 14, pp. 243-330, 10 pis. 

Meyrick, E. 

1912. Fam. Gracilariadae. Genera Insectorum, 128™*^ Fascicule. 

SCHAFFER, C. 

1889. Beitrage zur Histologic der Inseckten. Zoologische Jahrbiicher, Abth. flir Anatomic, Bd. Ill, 
Heft 4. 

Tower, W. L. 

1906. An Investigation of Evolution in Chrysomelid Beetles of the Genus Leptinotarsa. Carnegie 
Institution of Washington, Publication No. 48. 

Urech, F. 

1891. Beobachtungen liber die verschiedenen Schuppenfarben und die zeitHche Succession ihres 
Auftretens (Farbenfelderung) auf den Puppenflugelchen von Vanessa urticse und V. oi. 
Zool. Anz., Jahr. XIV, pp. 466-475. 



EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 167 



EXPLANATION OF PLATES III AND IV. 



PLATE III. 

Phylogenetic tree illustrating the evolution of the species of the "cylindrical-larval group 
and of Porphyrosela. (The figures on this and the following plate are three times natural size.) 



of Lithocolletis 



Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 



1. 
2. 
3. 

4. 
5. 
6. 

7. 

8. 

9. 

10. 



Fig. 11. 
Fig. 12. 
Fig. 13. 
Fig. 14. 
Fig. 15. 
Fig. 16. 
Fig. 17. 
Fig. 18. 
Fig. 19. 
Fig. 20. 
Fig. 21. 
Fig. 22. 
Fig. 23. 
Fig. 24. 
Fig. 25. 
Fig. 26. 
Fig. 27. 
Fig. 28. 
Fig. 29. 
Fig. 30. 
Fig. 31. 
Fig. 32. 
Fig. 33. 
Fig. 34. 
Fig. 35. 
Fig. 36. 
Fig. 37. 
Fig. 38. 
Fig. 39. 
Fig. 40. 
Fig. 41. 
Fig. 42. 
Fig. 43. 
Fig. 44. 
Fig. 45. 
Fig. 46. 
Fig. 47. 
Fig. 48. 
Fig. 49. 
Fig, 
Fig, 
Fig. 52. 
Fig. 53. 
Fig. 54. 
Fig. 55a. 
Fig. 555. 
Fig. 56. 
Fig. 57. 
Fig. 58. 



50. 
51. 



Liihocollelis tiliacella Cham. 

" oregonensis Wlsm. (not illustrated). 

" fragilella F. and B. 

" celtifoliella Cham. 

" tritcenianella Cham. 

" affinis F. and B. (not illustrated). 

" ostensackenella Fitch. 

" mariceella Cham. 

Porphyrosela desmodieUa Clem. 
Lithocolletis auronitens F. and B. 

argentinotella Clem. 

occitanica F. and B. (not illustrated). 

leucothorax Wlsm. 

fitchella Clem. 

salicifoliella Clem. 

tremMoidiella Braun. 

hageni F. and B. 

arhutusella Braun. 

insignis Wlsm. (not illustrated). 

insignis Wlsm. 

carycealhella Cham. 

rileyella Cham. 

ostrycEfoliella Clem. 

olivceformis Braun. 

ohscuricostella Clem. 

kearfottella Braun. 

populiella Cham. 

diaphaneUa F. and B. 

salicivorella Braun. 

deceptusella Cham. 

alni Wlsm. (not illustrated). 

alnicolella Wlsm. 

ledella Wlsm. 

incanella Wlsm. 

scudderella F. and B. 

cratcegella Clem. 

malimalifoliella Braun. 

propinquinella Braun. 

sexnotella Cham. 

aeriferella Clem. 

obsoleta F. and B. 

albanotella Cham. 

argentifimhriella Clem. 

lucidicostella Clem. 

clemensella Cham. 

quercialhella Fitch. 

trinotella Braun. 

morrisella Fitch. 

uhlerella Fitch. 

rohiniella Clem. 

lucetiella Clem. 

7nartieUa Braun. 

gemmea F. and B. 

symphoricarpella Cham. 

apicinigrella Braun. 

apicinigrella Braun. 

celtisella Cham. 

basistrigella Clem. 

hatavietla Braun. 



168 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS, 





PLATE 


IV 


Phylogenetic tree illustrating the evolution of the 


spe 


group '^ of Lithocolletis. 




Fig. 59a. Cremastohombycia grindeliella Wlsm. 




Fig. 595. 


" grindeliella Wlsm. 




Fig. 60. 


" solidaginis F. and B. 




Fig. 61. 


" ambrosiella Cham. 




Fig. 62. 


" ignota F. and B. 




Fig. 63. 


" verbesinella Busck. 




Fig. 64. Lithocolleiis ohstrictella Clem. 




Fig. 65. 


' tubiferella Clem. 




Fig. 66. 


' aceriella Clem. 




Fig. 67. 


' hamameliella Busck, 




Fig. 68. 


' ostryarella Cham. 




Fig. 69. 


' corylisella Cham. 




Fig. 70. 


' cesculisella Cham. 




Fig. 71. 


' guttifinitella Clem. 




Fig. 72. 


' carycefoliella Clem. 




Fig. 73. 


' lentella Braun. 




Fig. 74. 


' macrocarpella F. and B. 




Fig. 75. 


' cincinnatiella Cham. 




Fig. 76. 


' saccharella Braun. 




Fig. 77. 


' hamadryadella Clem. 




Fig. 78. 


' umbellularim Wlsm. 




Fig. 79. 


' agrifoliella Braun. 




Fig. 80. 


' fletcherella Braun. 




Fig. 81. ' 


' arcuella Braun. 




Fig. 82. 


' betulivora Wlsm. 




Fig. 83. 


' australisella Cham. 




Fig. 84. 


' belhunella Cham. 




Fig. 85. 


' chambersella Wlsm. 




Fig. 86. 


' cervina Wlsm. 




Fig. 87. 


' platanoidiella Braun. 




Fig. 88. 


' castaneceella Cham. 




Fig. 89. 


' fasciella Wlsm. 




Fig. 90. 


' nemoris Wlsm. 




Fig. 91. 


' gaultheriella Wlsm. 




Fig. 92. 


' mediodor sella Braun. 




Fig. 93. 


' quercivorella Cham. 




Fig. 94. 


' conglomeratella Zell. 




Fig. 95. 


' ulmella Cham. 





flat-larval 



JOURN. ACAD. NAT. SCI. PHILA., 2ND SEP., VOL. XVI. 



PLATE III 



f *. 





•,!f^-»~ 



hT 








^*jg5^ff# 



f . 



alnv 
31 




\ 32 





^'S* 



^ 



^ 



W 





m 



-'' ^^^P >7f>>'» f^^#. 





t""\: — '' 




I ■'> 


■^ 


1 'i 5/ 


28 


1 ^^^ 


'f^ ^m€^' 


\ f^ 


iG ,n 






r:^^ 


' 14 


13 




. occitanica 


nm 


12 



\ 



$p^ 




19 



3)^ 





^ 




Jypical cl^lkocollet^i 
Priimtivc Clncestor 



:tK 



oreqonensis 
2 



Seiren Unijormlij Colored Transverse Bands. 



X, 



A.KB. del. 



^ y ^ Lremastoiaom/bivcia 

ulcLi - 1 xrvaiUroap 




m^ 



affini£ 




f^ 



BRAUN: Color Patterns in Lithocolletis. 



JOURN. ACAD. NAT. SCI. PHILA., 2ND SER., VOL. XVI. 



PLATE IV. 



'K^ 



^ f* 



M^ 



r-^' i 



I ^^ t 



:>!^- 




^ 



^^;^ 



J Lat-larval Cjroup 



«;>.*^^ 



Q^., -^ 



rr^^^ 



r 



y^ 



few^ 






^ 



!?)«»' 



"^ « 




">», 





^ 







63 



/^■StT^. 



C r e 771 a s 1 boTTi bi^c I (2/ 



^ s:^r^- 



rrimitive Cincestor 



Ak 



Oeven ilrLijormlij Lolored Jransverse JJand: 
Jijpical jLitnocoiteti^ 



BRAUN: Color Patterns in LithocoHetis.